本論文旨在研究一維碳化鎢(W2C)及氧化鎢(W18O49)奈米線之成長製備以及其相關物性及化性特性的瞭解。在研究中，經由一簡易之爐管熱處理製程，在適當的實驗條件下可於以直流濺鍍法所沈積之鎢基金屬薄膜(W、WCx、及WOx)上自組成長出高密度之奈米線，並且，於實驗中透過各項物性及化性分析工具，如SEM、TEM、SAED、XRD、XPS、及Gaussian deconvolution等，對奈米線及薄膜本身進行製備特性及成分結構之瞭解。此外，於研究中並進行奈米線之場致發射特性(FE)電壓電流特性曲線的量測及相關特性參數之萃取。經由進一步探討薄膜中碳(C)/氧(O)對二元(W-O)及三元素(W-C-O)系統之鎢基薄膜(W、WCx、WOx、WCOx)表面奈米型態的影響後，並於本研究中提出相關成長主導機制之說明。
本實驗中，藉由於氮氣(N2)環境下熱處理的過程，可於濺鍍沈積之碳化鎢(WCx)薄膜上成長含碳化鎢(W2C)晶相之一維奈米線，在700℃的成長溫度下，所得之奈米線成長密度介於250-260 μm-2，其長度與管徑則分別介於0.2-0.3 μm與13-15 nm之間；並經由場發射電壓電流特性之量測可得知，對650℃及 700℃的試片而言，所得奈米線之場發射特性於電流密度為1 μA/cm2情況下之起始電場分別2.1及1.7 V/μm，所萃取出之電場增強因子(β)則分別介於4267-4998及5413-6339之間，由此得知其具備良好場發射特性，可供未來相關領域場發射源之應用。而經由XRD分析，可推測此碳化鎢(W2C)晶相之形成，與碳化鎢(WCx)薄膜於熱退火過程中之薄膜去碳過程有關。
進一步於實驗中調變熱處理溫度與時間以探究碳化鎢奈米線之製程溫度、時間窗口，得知於氮氣(N2)環境下其成長溫度及時間範圍分別介於500-750℃及2.5 -0.25小時之間，且於此製程窗口區間所得之奈米線管徑、長度、與成長密度則分別介於10-15 nm、0.1-0.3 μm、以及 210-410 μm-2之間，就趨勢而言，溫度越低所需之成長時間較長，奈米線晶粒小且奈米線成長密度較高，而超出上述相關製程窗口奈米線則有成長不全及消退之現象。由相關分析並可發現上述所提及之碳化鎢(WCx)薄膜去碳過程與奈米線之型態及成長密度相關。
本實驗亦嘗試高純度氧化鎢(W18O49)奈米線之成長製備，並由本研究之前期研究經驗得知直接在高溫條件(> 600℃)下於氧氣(O2)或氮氧(N2/O2)混合氣氛下，以熱退火方式均不易成長氧化鎢(W18O49)奈米線。故研究中提出一種以熱退火/氧化之兩階段製程，先將碳化鎢(WCx)薄膜於680℃、30分鐘的條件下於氮氣(N2)環境中成長含碳化鎢晶相之奈米線成核點，之後再於較低溫度之450℃、30分鐘的條件下，於氧氣(O2)氣氛中將該奈米線之成核點成長轉化為W18O49(010) 單斜晶系氧化鎢奈米線，所得之氧化鎢奈米線氧化程度高且結晶性良好，其長度與線徑分別介於0.15-0.2 μm與10-20 nm之間，薄膜表面氧化鎢奈米線晶粒密度高，具高有效感測表面積，並由於薄膜本身氧化程度亦完整，故此一製備方式極適合於阻值變動感測型氧化鎢氣體感測器領域使用。而實驗中各項分析結果顯示，薄膜中碳(C)原子持續地於熱退火過程中析出與氧(O)原子於較低溫度之置換過程，為此兩階段氧化鎢奈米線製備成長之關鍵因素。
為進一步瞭解氧(O)原子於W18O49(010) 單斜晶氧化鎢奈米線以熱處理方式成長過程中所扮演之角色與地位，本研究嘗試於鎢(W)金屬薄膜直流濺鍍沈積過程中，藉由調變氧氣/氬氣(O2/Ar)氣體流量比例(OAFRR)，而對鎢(W)金屬薄膜進行較有限量之氧(O)原子摻雜，之後將所沈積之薄膜於氮氣(N2)環境下進行熱退火處理。研究結果顯示，於700-850℃、15 分鐘、流量比例為0/24的條件下，可於鎢(W)金屬薄膜上成長出結晶性佳之W18O49(010) 氧化鎢奈米線；而當氧氣/氬氣(O2/Ar)氣體流量比例提高至1/24時，則可觀察到明顯之氧化鎢奈米線消退現象，溫度越高其消退現象愈為明顯；當該流量比例調高至2/24與4/24時，上述之氧化鎢奈米線幾乎完全消退殆盡，試片表面僅存結晶晶界痕跡而趨於平坦；而流量比例提高至6/24時，此時奈米片狀結構開始出現，試片表面片狀物與線狀物共存；進一步提高該流量比例至8/24，此時所沈積薄膜內氧含量約為55 at%，於退火後則可觀察到大量大尺寸氧化鎢奈米片狀結構的出現。由於，奈米線狀結構於本實驗中主要於低氧氣/氬氣(O2/Ar)分壓(0/24、1/24)時出現，此一結果與前述於高溫下(> 600℃)不易於氧氣(O2)或氮氧(N2/O2)混合氣氛下直接成長氧化鎢奈米線之趨勢一致，更說明了於以熱退火方式成長奈米線時，奈米線之成長對氧量有一低的臨界上限，過量之氧(O)原子其不利於氧化鎢奈米線成長之重要結果。而各項儀器分析結果亦顯示，在氧氣/氬氣(O2/Ar)調變過程中，所沈積之鎢(W)金屬薄膜於大氣環境下表面所吸附之氧(O)、沈積過程所摻入之氧(O)含量以及薄膜本身之結晶特性，為影響氧化鎢奈米線成長消退之重要因素。
最後，可總結地發現經由以濺鍍法沈積製備之鎢金屬相關薄膜，即便是鎢(W)或碳化鎢(WCx)薄膜，於濺鍍沈積過程中薄膜表面、及內部氧(O)原子的引入均勢所難免，故經由進一步探討薄膜中碳(C)/氧(O)對二元(W-O)及三元素(W-C-O)系統之鎢基薄膜(W、WCx、WOx、WCOx)表面奈米型態的影響後，吾人發現對僅含鎢(W)、氧(O)之二元素薄膜(W、WOx)而言，薄膜的微結晶結構主導了低氧分壓(OAFRR 0-2/24)時奈米線之消退現象，而相對多量之氧(OAFRR>6/24)則主導了大尺寸奈米片狀結構的出現；另外，對三元素薄膜(WCx、WCOx)而言，於低氧分壓(OAFRR 0/24)時，碳(C)原子的加入將使奈米線狀結構之成長密度下降，此一現象推測亦與薄膜之結晶結構有關，而在高氧分壓(OAFRR>6/24)時，則可發現三元素(W-C-O)薄膜系統中碳(C)原子於高溫退火過程中之熱析出(out-diffusion)現象將有助於奈米片狀結構之增長。

In this thesis, the growth and physical/chemical properties of one-dimensional tungsten carbide (W2C) and tungsten oxide (W18O49) nanowires were investigated. Nanowires were self-synthesized on sputter-deposited tungsten based (W, WCx, WOx) thin films after a simple thermal annealing process in N2 ambient. Techniques of various analyses including SEM, TEM, SAED, XRD, XPS, and Gaussian deconvolution were employed to characterize the growing conditions and properties of nanowires. The electric field emission properties of nanowires were measured. The influence of oxygen/carbon atoms on the self-synthesis and surface morphologies of W-O binary (W, WOx) and W-C-O ternary (WCx, WCOx) reacting thin films were also discussed, and then the possible dominant growing mechanism was proposed.
First, the growth of dense W2C nanowires by a simple thermal annealing of sputter-deposited WCx films in N2 ambient is reported. Straight nanowires with a density of 250-260 micron meter-2 and length/diameter in the range of 0.2-0.3 micron meter/13-15 nm were obtained from the 700oC-annealed samples. For 650 and 700oC-annealed samples, the turn-on electric filed at the current density of 1 micron Ampere/cm2 were 2.1 and 1.7 V/micron meter, respectively. The enhancement factor (beta) is in the range of 4267-6339, which exhibits good electron field emission characteristics for the application of field emitters. The self-catalytic growth of W2C nanowires is attributed to the formation of alpha-W2C phase caused by carbon depletion in the WCx films during thermal annealing in N2 ambient.
The details of thermal annealing conditions in N2 ambient for the self-synthesis of tungsten carbide nanowires from sputter-deposited WCx films were also investigated. Experimental results show that the temperature window for the growth of nanowires lies in the range of 500-750oC with the corresponding annealing time interval ranging from 2.5-0.25 hr. The diameter, length, and density of the grown nanowires are in the range of 10-15 nm, 0.1-0.3 micron meter, and 210-410 micron meter-2, respectively. The degree of carbon depletion in the annealed WCx films plays a crucial role in determining both the shape and density of the self-synthesized nanowires. Nanowires synthesized at lower temperatures were seen smaller in dimension but higher in density. Material analysis reveals that the phase transition from WC to W2C arising from the decarburization of WCx films during thermal annealing should be responsible for the self-synthesis of nanowires.
The preparation of tungsten oxide nanowires was also studied in our work. From the prior study of our research, it is found that tungsten oxide (W18O49) nanowires were not easily to be obtained through the annealing process in O2 or N2/O2 gas mixture ambient at high temperatures (> 600oC). Therefore, the self-synthesis of tungsten oxide nanowires on sputter-deposited WCx films using a simple annealing/oxidization process was reported. It was found that thermal annealing of WCx films at 680oC for 30 min in N2 followed by the oxidation at 450oC for 30 min in pure oxygen would yield dense and well crystallized monoclinic W18O49 (010) nanowires with typical length/diameter of about 0.15-0.2 micron meter/10-20 nm. The combination step of process shows its potential in the application field of gas sensors due to highly oxidized thin films and enormous surface area of nanowires. The formation of W18O49 nanowires is attributed to the nuclei of immature W2C nanowires experienced a re-growth process, accompanying with carbon depletion and the oxidization of tungsten during the subsequent oxidization process.
In order to realize the role of oxygen in the growth of tungsten oxide nanowires, influence of O2/Ar flow rate ratios (OAFRRs) in the sputtering gas on the self-synthesis of tungsten oxide (W18O49) nanowires on sputter-deposited W films was studied. After thermally annealing at 700-850oC in N2 ambient for 15 min, dense and well crystalline W18O49 (010) nanowires or nano-belts were obtained depending on the oxygen content in the sputtering gas. Experimental results show that the annealing temperature required for the full growth of W18O49 nanowires reduced when the OAFRR in the sputtering gas was increased. It is found the oxygen absorbed in the surface region is responsible for the growth of nanowires. For OAFRR of 0/24, dense and well crystalline W18O49 (010) nanowires were obtained, however obvious collapse of nanowires was seen as the OAFRR increased to 1/24. The collapse was more severe with increasing the annealing temperature. When the OAFRR was 2/24 and 4/24, nearly only flat grains were seen on the surface of samples. As the OAFRR increased to 6/24, sheet structure of tungsten oxide appeared and coexisted with nanowires. Further increased the OAFRR to 8/24, which resulted in an saturated oxygen content of about 55 at% inside the W film, large-scale nano-belts or nano-sheets of W18O49 were grown. The nanowire structure mainly occurred at the relatively low OAFRRs of 0/24 and 1/24. This result infers the fact mentioned above that tungsten oxide nanowire would not be preferable grown directly in O2 or N2/O2 ambient. Too much amount of oxygen would be harmful to growing tungsten oxide nanowires. In addition, results of material analysis also revealed that the absorption of oxygen on surface, oxygen content in thin films, and the microstructure/texture of as-deposited tungsten films prepared with different OAFRRs should dominate the evolution from nanowires to nano-belts as the OAFRR was changed.
Finally, it was found that the introducing of oxygen (O) atoms in sputter-deposited W-based thin films was unavoidable even for W and WCx films. Therefore, the investigation of oxygen/carbon atoms on the self-synthesis and surface morphologies of W-O binary (W, WOx) and W-C-O ternary (WCx, WCOx) reacting films were also discussed. For W-O binary system of W and WOx films, the nano-crystallization of the films dominated the collapse of nanowires at OAFRR of 0-2/24. The relatively high OAFRR of above 6/24 dominated the occurrence of large scale sheet structure. For W-C-O ternary system of WCx and WCOx films, the introducing of carbon (C) atoms would lead the decrease of wire density at low OAFRR of 0/24. This phenomenon could also be attributed to the nano-crystallization of thin films. Moreover, the out-diffusion process of carbon (C) atoms was found to enhance the growing of sheet structure under high OAFRRs of above 6/24.

References of Chapter 1
[1] George Elling, Managing Director, Deutsche Bank Technology Group, “THE NANOTECH REPORT 2003”, Investment Overview and Market Research for Nanotechnology (Volume II).
[2] http://www.er.doe.gov/production/bes/scale_of_things.html
[3] S. Iijima, “Helical microtubules of graphitic carbon”, Nature 354, 56 (1991).
[4] http://www.tipmagazine.com/tip/INPHFA/vol-10/iss-1/p24.html
[5] T. Kato, G. H. Jeong, T. Hirata, R. Hatakeyama, K. Tohji, and K. Motomiya, “Single-walled carbon nanotubes produced by plasma-enhanced chemical vapor deposition”, Chem. Phys. Lett. 381, 422 (2003).
[6] S. Y. Chen, H. Y. Miao, J. T. Lue, and M. S. Ouyang, “Fabrication and field emission property studies of multiwall carbon nanotubes”, J. Phys. D: Appl. Phys. 37, 273 (2004).
[7] G. H. Jeong, T. Izumida, T. Hirata, R. Hatakeyama, Y. Neo, H. Mimura, K. Omote, Y. Kasama, S. H. Jhang, and Y. W. Park, “Electric transport properties of single-walled carbon nanotubes functionalized by plasma ion irradiation method”, 4th IEEE Conference on Nanotechnology (2004).
[8] P. N. Gevko, A. V. Okotrub, T. A. Duda, G. Z. Khamidullina, L. G. Bulusheva, V. V. Belavin, and I. V. Yushina, “Optical absorption of single-wall carbon nanotubes produced by arc-discharge method with different concentration of Ni/Co catalyst”, Fullerenes, Nanotubes, and Carbon Nanostructures 12, 287 (2004).
[9] W. B. Choi, D. S. Chung, J. H. Kang, H. Y. Kim, Y. W. Jin, I. T. Han, Y. H. Lee, J. E. Jung, N. S. Lee, G. S. Park, and J. M. Kim, “Fully sealed, high-brightness carbon-nanotube field-emission display”, Appl. Phys. Lett. 75, 3129 (1999).
[10] X. F. Duan, Y. Huang, Y. Cui, J. F. Wang, and C. M. Lieber, “Indium phosphide nanowires as building blocks for nanoscale electronic and optoelectronic devices “, Nature 409, 66 (2001).
[11] M. Yoshida, M. Lal, N. D. Kumar, and P. N. Prasad, “TiO2 nano-particle-dispersed polyimide composite optical waveguide materials through reverse micelles”, J. Mat. Sci. 32, 4047 (1997).
[12] H. J. Dai, E. W. Wong, Y. Z. Lu, S. S. Fan, and C. M. Lieber, “Synthesis and characterization of carbide nanorods”, Nature 375, 769 (1995).
[13] Z. W. Pan, Z. R. Dai, and Z. L. Wang, “Nanobelts of Semiconducting Oxides” Science 291, 1947 (2001).
[14] H. Ibach, and H. Luth, Solid State Physics, Springer, Berlin, Heidelberg, New York, 1996.
[15] R. Waser, Nanoelectronics and Information Technology, Wiley, Germany, 2003.
[16] H. Sakaki, G. Yusa, T. Someya, Y. Ohno, T. Noda, H. Akiyama, Y. Kadoya, and H. Noge, “Transport properties of two-dimensional electron gas in AlGaAs/GaAs selectively doped heterojunctions with embedded InAs quantum dots”, Appl. Phys. Lett. 67, 3444 (1995).
[17] S. Schmitt-Rink, D. S. Chemla, and D. A. B. Miller, “Linear and nonlinear optical properties of semiconductor quantum wells”, Adv. Phys. 38, 89 (1989).
[18] S. J. Tans, M. H. Devoret, H. Dai, A. Thess, R. E. Smalley, L. J. Geerligs, and C. Dekker, “Individual single-wall carbon nanotubes as quantum wires”, Nature 386, 474 (1997).
[19] R. Mirin, A. Gossard, and J. Bowers, “Room temperature lasing from InGaAs quantum dots”, Elect. Lett. 32, 1732 (1996).
[20] H. Grabert, and M. Devoret, Single Electron Tunneling, Plenum Press, New York, (1992).
[21] D. L. Feldhein, and C. D. Keating, “Self-assembly of single electron transistors and related devices”, Chem. Soc. Rev. 27, 1 (1998).
[22] K. Yano, T. Ishii, T. Hashimoto, T. Kobayashi, F. Murai, and K. Seki, “Room-temperature single-electron memory”, IEEE Transactions on Electron Devices 41, 1628 (1994).
[23] S. H. Wang, T. C. Chou, and C. C. Liu, “Nano-crystalline tungsten oxide NO2 sensor”, Sens. and Actuators B 94, 343 (2003).
[24] C. Bock, C. Paquet, M. Couillard, G. A. Botton, and B. R. MacDougall, “Size-selected synthesis of PtRu nano-catalysts: reaction and size control mechanism”, J. Am. Chem. Soc. 126, 8028 (2004).
[25] R. R. Vanfleet, and J. M. Mochel, “Thermodynamics of melting and freezing in small particles”, Surf. Sci. 341, 40 (1995).
[26] S. L. Lai, J. Y. Guo, V. Petrova, G. Ramanath, and L. H. Allen, “Size-dependent melting properties of small Tin particles: nanocalorimetric measurements”, Phys. Rev. Lett. 77, 99 (1996).
[27] K. F. Peters, Y. W. Chung, and J. B. Cohen, “Surface melting on small particles”, Appl. Phys. Lett. 71, 2391, (1997).
[28] M. Wautelet, “Size effect on the melting (or disordering) temperature of small particles”, Solid State Commun. 74, 1237 (1990).
[29] T. Castro, R. Reifenberger, E. Choi, and R. P. Andres, “Size-dependent melting temperature of individual nanometer-sized metallic clusters”, Phys. Rev. B 42, 8548 (1990).
[30] A. N. Goldstein, C. M. Echer, and A. P. Alivisatos, “Melting in semiconductor nanocrystals”, Science 256, 1425 (1992).
[31] G. L. Allen, R. A. Bayles, W. W. Gile, and W. A. Jesser, “Small particle melting of pure metals”, Thin Solid Films 144, 297 (1986).
[32] Ph. Buffat, and J. P. Borel, “Size effect on the melting temperature of gold particles”, Phys. Rev. A 13, 2287 (1976).
[33] E. O. Hall, Proc. Phys. Soc. Ser. B, 64, 747 (1951).
[34] N. J. Petch, J. Iron and Steel Inst. 174, 25 (1953).
[35] T. G. Nieh, and J. Wadsworth, Scripta Met. 25, 955 (1991).
[36] H. Hahn, P. Mondal, and K. A. Padmanabhan, “Plastic deformation of nanocrystalline materials”, NanoStruct. Mater. 9, 603 (1997).
[37] P. A. Cox, “Transition Metal Oxides”, Clarendon Press, Oxford (1995).
[38] P. Woodward, and A. Sleight, “Ferroelectric tungsten oxide”, J. Sol. State Chem., 131, 9 (1997).
[39] A. Souza-Filho, V. Freire, J. Sasaki, J. Mendes-Filho, J. Juliao, and U. Gomes, “Coexistence of triclinic and monoclinic phases in WO3 ceramics”, J. Raman Spect., 31, 451 (2000).
[40] Z. Xu, J. F. Vetelino, R. Lec, D. C. Parker, “Electrical properties of tungsten trioxide films”, J. Vac. Sci. Technol. A 8, 3634 (1990).
[41] R. W. Wood, “A new form of cathode discharge and the production of X-rays, together with some notes on diffraction”, Phys. Rev. 5, 1 (1897).
[42] R. H. Fowler, L. W. Nordheim, Proc. R. Soc. London Ser. A 119, 173 (1928).
[43] W. A. de Heer, A. Chatelain, and D. Ugarte, “A carbon nanotube field-emission electron source”, Science 270, 1179 (1995).
[44] B. S. Satyanarayana, A. Hart, W. I. Milne, and J. Robertson, “Field emission from tetrahedral amorphous carbon”, Appl. Phys. Lett. 71, 1430 (1997).
[46] C. Lea, “Field emission from carbon fibers”, J. Phys. D, 6, 1105 (1973).
[47] A. G. Rinzler, J. H. Hafner, P. Nikolaev, L. Lou, S. G. Kim, D. Tomanek, P. Nordlander, D. T. Colbert, and R. E. Smalley, “Unraveling nanotubes: field emission from an atomic wire”, Science 269, 1550 (1995).
[48] J. C. Charlier, M. Terrones, M. Baxendale, V. Meunier, T. Zacharia, N. L. Rupesinghe, W. K. Hsu, N. Grobert, H. Terrones, and G. A. J. Amaratunga, “Enhanced electron field emission in B-doped carbon nanotubes”, Nano Lett. 2, 1191 (2002).
[49] Y. H. Lee, C. H. Choi, Y. T. Jang, E. K. Kim, B. K. Ju, N. K. Min, and J. H. Ahn, “Tungsten nanowires and their field emission properties”, Appl. Phys. Lett. 81, 745 (2002).
[50] X. Yang, M. L. Simpson, S. J. Randolph, P. D. Rack, L. R. Baylor, H. Cui, and W. L. Gardner, “Integrated tungsten nanofiber field emission cathodes selectively grown by nanoscale electron beam-induced deposition”, Appl. Phys. Lett. 86, 183106 (2005).
[51] J. P. Singh, F. Tang, T. Karabacak, T. M. Lu, and G. C. Wang, “Enhanced cold field emission from (100) oriented -W nanoemitters”, J. Vac. Sci. Technol. B 22, 1048 (2004).
[52] A. G. Umnov, Y. Shiratori, and H. Hiraoka, “Giant field amplification in tungsten nanowires”, Appl. Phys. A 77, 159 (2003).
[53] T. Arie, S. Akita, and Y. Nakayama, “Growth of tungsten carbide nano-needle and its application as a scanning tunneling microscope tip”, J. Phys. D 31, L49 (1998).
[54] Y. Li, Y. Bando, and D. Golberg, “Quasi-aligned single-crystalline W18O49 nanotubes and nanowires”, Adv. Mater. 15, 1294 (2003).
[55] J. Zhou, L. Gong, S. Z. Deng, J. Chen, J. C. She, N. S. Xu, R. Yang, and Z. L. Wang, “Growth and field-emission property of tungsten oxide nanotip arrays”, Appl. Phys. Lett. 87, 223108 (2005).
[56] J. Liu, Z. Zhang, Y. Zhao, X. Su, S. Liu, and E. Wang, “Tuning the field-emission properties of tungsten oxide nanorods”, Small 1, 310 (2005).
[57] C. Y. Zhi, X. D. Bai, and E. G. Wang, “Enhanced field emission from carbon nanotubes by hydrogen plasma treatment”, Appl. Phys. Lett. 81, 1690 (2002).
[58] Z. S. Wu, S. Z. Deng, N. S. Xu, J. Chen, J. Zhou, and J. Chen, “Needle-shaped silicon carbide nanowires: synthesis and field electron emission properties”, Appl. Phys. Lett. 80, 3829 (2002).
[59] Y. B. Li, Y. Bando, and D. Golberg, “MoS2 nanoflowers and their field-emission properties”, Appl. Phys. Lett. 82, 1962 (2003).
[60] J. Chen, S. Z. Deng, S. H. Wang, X. G. Wen, S. H. Yang, C. L. Yang, J. N. Wang, and W. K. Ge, “Field emission from crystalline copper sulphide nanowire arrays”, Appl. Phys. Lett. 80, 3620 (2002).
[61] L. Nilsson, O. Groening, C. Emmemegger, O.Kuettel, E. Schaller, L. Schlapbach, H. Kind, J. M. Bonard, and K. Kern, “Scanning field emission from patterned carbon nanotube films”, Appl. Phys. Lett. 76, 2071 (2000).
[62] J. S. Suh, K. S. Jeong, and J. S. Lee, “Study of the field-screening effect of highly ordered carbon nanotube arrays”, Appl. Phys. Lett. 80, 2392 (2002)
[63] A. Wei, X. W. Sun, C. X. Xu, Z. L. Dong, M. B. Yu, and W. Huang, “Stable field emission from hydrothermally grown ZnO nanotubes”, Appl. Phys. Lett. 88, 213102 (2006).
[64] Y. H. Yang, C. X. Wang, B. Wang, N. S. Xu, and G. W. Yang, “ZnO nanowire and amorphous diamond nanocomposites and field emission enhancement”, Chem. Phys. Lett. 403, 248 (2005).
[65] L. Liao, J. C. Li, D. F. Wang, C. Liu, and Q. Fu, “Electron field emission studies on ZnO nanowires”, Mater. Lett. 59, 2465 (2005).
[66] C. X. Xu and X. W. Sun, “Field emission from zinc oxide nanopins”, Appl. Phys. Lett. 83, 3806 (2003).
[67] B. Zeng, G. Xiong, S. Chen, S. H. Jo, W. Z. Wang, D. Z. Wang, and Z. F. Ren, “Field emission of silicon nanowires”, Appl. Phys. Lett. 88, 213108 (2006).
[68] S. Q. Li, Y. X. Liang, and T. H. Wang, “Nonlinear characteristics of the Fowler–Nordheim plot for field emission from In2O3 nanowires grown on InAs substrate”, Appl. Phys. Lett. 88, 53107 (2006).
[69] S. Luo, P. K. Chu, Z. Di, M. Zhang, W. Liu, C. Lin, J. Fan, and X. Wu, “Vacuum electron field emission from SnO2 nanowhiskers annealed in N2 and O2 atmospheres”, Appl. Phys. Lett. 88, 13109 (2006).
[70] Q. Zhao, J. Xu, X. Y. Xu, Z. Wang, and D. P. Yu, “Field emission from AlN nanoneedle arrays”, Appl. Phys. Lett. 85, 5331 (2004).
[71] D. H. Kim, H. S. Jang, H. R. Lee, C. D. Kim, and H. D. Kang, “Field emission properties of vertically aligned iron nanocluster wires grown on a glass substrate”, Appl. Phys. Lett. 85, 109 (2004).
[72] T. J. Vink, M. Gillies, J. C. Kriege, and H. W. J. J. van de Laar, “Enhanced field emission from printed carbon nanotubes by mechanical surface modification”, Appl. Phys. Lett. 83, 3552 (2003).
[73] T. Jeong, J. Heo, J. Lee, S. Lee, W. Kim, H. Lee, S. Park, J. M. Kim, T. Oh, C. Park, J. B. Yoo, B. Gong, N. Lee, and S. Yu, “Improvement of field emission characteristics of carbon nanotubes through metal layer intermediation”, Appl. Phys. Lett. 87, 63112 (2005).

References of Chapter 3
[1] N. A. Fox, W. N. Wang, T. J. Davis, J. W. Steeds, and P. W. May, “Field emission properties of diamond films of different qualities”, Appl. Phys. Lett. 71, 2337 (1997).
[2] M. W. Geis, J. C. Twichell, N. N. Efremow, K. Kroho, and T. M. Lysczarz, “Comparison of electric field emission from nitrogen-doped, type Ib diamond, and boron-doped diamond”, Appl. Phys. Lett. 68, 2294 (1996).
[3] J. Robertson, “Mechanisms of electron field emission from diamond, diamond-like carbon, and nanostructured carbon”, J. Vac. Sci. Technol. B 17, 659 (1999).
[4] S. R. P. Silva, G. A. J. Amaratunga, and J. R. Barnes, “Self-texturing of nitrogenated amorphous carbon thin films for electron field emission”, Appl. Phys. Lett. 71, 1477 (1997).
[5] J. D. Carey, R. D. Forrest, and S. R. P. Silva, “Origin of electric field enhancement in field emission from amorphous carbon thin films”, Appl. Phys. Lett. 78, 2339 (2001).
[6] W. A. de Heer, A. Chatelain, and D. Ugarte, “A carbon nanotube field-emission electron source”, Science 270, 1179 (1995).
[7] Y. Chen, S. Patel, Y. Ye, D. T. Shaw, and L. Guo, “Field emission from aligned high-density graphitic nanofibers”, Appl. Phys. Lett. 73, 2119 (1998).
[8] J. K. N. Lindner, W. M. Tsang, S. P. Wong, J. B. Xu, and I. H. Wilson, “XTEM characterization of tungsten implanted SiC thin films on silicon for field emission devices”, Thin Solid Films 427, 417 (2003).
[9] C. T. Hseih, J. M. Chen, H. H. Lin, and H. C. Shih, “Field emission from various CuO nanostructures”, Appl. Phys. Lett. 83, 3383 (2003)
[10] J. J. Li, W. T. Zheng, Z. S. Jin, X. Wang, H. J. Bian, G. R. Gu, Y. N. Zhao, S. H. Meng, X. D. He, and J. C. Han, “Electron field emission of radio frequency magnetron sputtered CNx films annealed at different temperatures”, J. Vac. Sci. Technol. B 21, 2382 (2003).
[11] S. J. Wang, H. Y. Tsai, and S. C. Sun, “A comparative study of sputtered TaCx and WCx films as diffusion barriers between Cu and Si”, Thin Solid Films 394, 179 (2001).
[12] S. J. Wang, H. Y. Tsai, and S. C. Sun, “Characterization of tungsten carbide as diffusion barrier for Cu metallization”, Jpn. J. Appl. Phys. Part 1 40, 2642 (2001).
[13] S. J. Wang, H. Y. Tsai, and S. C. Sun, “Characterization of sputtered titanium carbide film as diffusion barrier for copper metallization”, J. Electrochem. Soc. 148, 563 (2001).
[14] S. J. Wang, H. Y. Tsai, S. C. Sun, and M. H. Shiao, “Thermal stability of sputtered tungsten carbide as diffusion barrier for copper metallization”, J. Electrochem. Soc. 148, G500 (2001).
[15] Y. H. Lee, C. H. Choi, Y. T. Jang, E. K. Kim, B. K. Ju, N. K. Min, and J. H. Ahn, “Tungsten nanowires and their field electron emission properties”, Appl. Phys. Lett. 81, 745 (2002).
[16] B. S. Satyanarayana, A. Hart, W. I. Milne, and J. Robertson, “Field emission from tetrahedral amorphous carbon”, Appl. Phys. Lett. 71, 1430 (1997).
[17] J. M. Kim, W. B. Choi, N. S. Lee, and J. E. Jung, “Field emission from carbon nanotubes for displays”, Diamond and Related Materials 9, 1184 (2000).
[18] J. S. Lee, and J. S. Suh, “Uniform field emission from aligned carbon nanotubes prepared by CO disproportionation”, J. Appl. Phys. 92, 7519 (2002).
[19] X. Xu, and G. R. Brandes, “A method for fabricating large-area, patterned, carbon nanotube field emitters”, Appl. Phys. Lett. 74, 2549 (1999).
[20] H. Romanus, V. Cimalla, J. A. Schaefer, L. Spieb, G. Ecke, and J. Pezoldt, “Preparation of single phase tungsten carbide by annealing of sputtered tungsten-carbon layers”, Thin Solid Films 359, 146 (2000).

References of Chapter 4
[1] S. Iijima, “Helical microtubules of graphitic carbon”, Nature 354, 56 (1991).
[2] X. F. Duan, Y. Huang, Y. Cui, J. F. Wang, and C. M. Lieber, “Indium phosphide nanowires as building blocks for nanoscale electronic and optoelectronic devices “, Nature 409, 66 (2001).
[3] Z. W. Pan, Z. R. Dai, and Z. L. Wang, “Nanobelts of Semiconducting Oxides” Science 291, 1947 (2001).
[4] H. J. Dai, E. W. Wong, Y. Z. Lu, S. S. Fan, and C. M. Lieber, “Synthesis and characterization of carbide nanorods”, Nature 375, 769 (1995).
[5] N. S. Lee, D. S. Chung, J. H. Kang, H. Y. Kim, S. H. Park, Y. W. Jin, Y. S. Choi, I. T. Han, N. S. Park, M. J. Yun, J. E. Jung, C. J. Lee, J. H. You, S. H. Jo, C. G. Lee, and J. M. Kim, “Carbon nanotube-based field-emission displays for large-area and full-color applications”, Jpn. J. Appl. Phys. 39, 7154 (2000).
[6] H. W. C. Postma, T. Teepen, Z. Yao, M. Grifoni, and C. Dekker, “Carbon nanotube single-electron transistors at room temperature”, Science 293, 76 (2001).
[7] G. Che, B. B. Lakshmi, E. R. Fisher, and C. R. Martin, “Carbon nanotubule membranes for electrochemical energy storage and production”, Nature 393, 346 (1998).
[8] H. Kuramochi, K. Ando, Y. Shikakura, M. Yasutake, T. Tokizaki, and H. Yokoyama, “Nano-oxidation and in situ faradaic current detection using dynamic carbon nanotube probes”, Nanotechnology 15, 1126 (2004).
[9] X. H. Zhang, S. Y. Xie, Z. Y. Jiang, X. Zhang, Z. Q. Tian, Z. X. Xie, R. B. Huang, and L. S. Zheng, “Rational design and fabrication of ZnO nanotubes from nanowire templates in a microwave plasma system”, J. Phys. Chem. B 107, 10114 (2003).
[10] S. H. Yu, and M. Yoshimura, “Shape and phase control of ZnS nanocrystals: template fabrication of wurtzite ZnS single-crystal nanosheets and ZnO flake-like dendrites from a lamellar molecular precursor ZnS•(NH2CH2CH2NH2)0.5”, Adv. Mater. 14, 296 (2002).
[11] W. Han, S. Fan, Q. Li, and Y. Hu, “Synthesis of gallium nitride nanorods through a carbon nanotube-confined reaction”, Science 277, 1287 (1997).
[12] M. Iwata, K. Adachi, S. Furukawa, and T. Amakawa, “Synthesis of purified AlN nano powder by transferred type arc plasma”, J. Phys. D: Appl. Phys. 37, 1041 (2004).
[13] Y. H. Lee, C. H. Choi, Y. T. Jang, E. K. Kim, B. K. Ju, N. K. Min, and J. H. Ahn, “Tungsten nanowires and their field emission properties”, Appl. Phys. Lett. 81, 745 (2002).
[14] L. G. Teoh, I. M. Hung, J. Shieh, W. H. Lai, and M. H. Hon, “High sensitivity semiconductor NO2 gas sensor based on mesoporous WO3 thin film”, Electrochem. Solid State Lett. 6, G108 (2003).
[15] G. Gu, B. Zheng, W. Q. Han, S. Roth, and J. Liu, “Tungsten oxide nanowires on tungsten substrates”, Nano Lett. 2, 849 (2002).
[16] S. J. Wang, H. Y. Tsai, and S. C. Sun, “Characterization of tungsten carbide as diffusion barrier for Cu metallization”, Jpn. J. Appl. Phys. Part 1 40, 2642 (2001).
[17] T. Arie, S. Akita, and Y. Nakayama, “Growth of tungsten carbide nano-needle and its application as a scanning tunneling microscope tip”, J. Phys. D 31, L49 (1998).
[18] P. Hoyer, “Formation of a titanium dioxide nanotube array”, Langmuir 12, 1411 (1996).
[19] S. J. Wang, C. H. Chen, S. C. Chang, K. M. Uang, C. P. Juan, and H. C. Cheng, “Growth and characterization of tungsten carbide nanowires by thermal annealing of sputter-deposited WCx films”, Appl. Phys. Lett. 85, 2358 (2004).
[20] R. J. Colton, and J. W. Rabalais, “Electronic structure to tungsten and some of its borides, carbides, nitrides, and oxides by x-ray electron spectroscopy”, Inorg. Chem. 15, 236 (1976).
[21] H. Estrade-Szwarckopf, and B. Rousseau, “U.P.S. and X.P.S. studies of alkali-graphite intercalation compounds”, Synth. Met. 23, 191 (1988).

References of Chapter 5
[1] Y. Koltypin, S. I. Nikitenko, and A. Gedanken, “The sonochemical preparation of tungsten oxide nanoparticles”, J. Mater. Chem. 12, 1107 (2002).
[2] C. Santato, M. Odziemkowski, M. Ulmann, and J. Augustynski, “Crystallographically oriented mesoporous WO3 films: synthesis, characterization, and applications”, J. Am. Chem. Soc. 123, 10639 (2001).
[3] N. Renard, C. Sella, O. Nemraoui, M. Maaza, Y. Sampeur, and J. Lafait, “Preparation, characterization and properties of sputtered electrochromic and thermochromic devices”, Surf. Coat. Technol. 98, 1477 (1998).
[4] Y. Zhao, Z. C. Feng, and Y. Liang, “Pulsed laser deposition of WO3-base film for NO2 gas sensor application”, Sens. Actuators B 66, 171 (2000).
[5] H. Meixner, J. Gerblinger, U. Lampe, and M. Fleischer, “Thin-film gas sensors based on semiconducting metal oxides”, Sens. Actuators B 23, 119 (1995).
[6] J. L. Solis, S. Saukko, L. Kish, C. G. Granqvist, and V. Lantto, “Semiconductor gas sensors based on nanostructured tungsten oxide”, Thin Solid Films 391, 255 (2001).
[7] L. G. Teoh, I. M. Hung, J. Shieh, W. H. Lai, and M. H. Hon, “High sensitivity semiconductor NO2 gas sensor based on mesoporous WO3 thin film”, Electrochem. Solid State Lett. 6, G108 (2003).
[8] G. Gu, B. Zheng, W. Q. Han, S. Roth, and J. Liu, “Tungsten oxide nanowires on tungsten substrates”, Nano Lett. 2, 849 (2002).
[9] X. L. Li, J. F. Liu, and Y. D. Li, “Large-scale synthesis of tungsten oxide nanowires with high aspect ratio”, Inorg. Chem. 42, 921 (2003).
[10] J. Liu, Y. Zhao, and Z. Zhang, “Low-temperature synthesis of large-scale arrays of aligned tungsten oxide nanorods”, J. Phys.: Condens. Matter 15, L453 (2003).
[11] S. J. Wang, C. H. Chen, S. C. Chang, K. M. Uang, C. P. Juan, and H. C. Cheng, “Growth and characterization of tungsten carbide nanowires by thermal annealing of sputter-deposited WCx films”, Appl. Phys. Lett. 85, 2358 (2004).
[12] S. J. Wang, C. H. Chen, S. C. Chang, C. H. Wong, K. M. Uang, T. M. Chen, R. M. Ko, and B. W. Liou, “On the thermal annealing conditions for self-synthesis of tungsten carbide nanowires from WCx films”, Nanotechnology 16, 273 (2005).
[13] F. P. J. Kerkhof, J. A. Moulijn, and A. Heeres, “The XPS spectra of the metathesis catalyst tungsten oxide on silica gel”, J. Electron Spectrosc. Relat. Phenom. 14, 453 (1978).
[14] D. D. Sarma, and C. N. R. Rao, “XPES studies of oxides of second- and third-row transition metals including rare earths”, J. Electron Spectrosc. Realt. Phenom. 20, 25 (1980).
[15] R. J. Colton, and J. W. Rabalais, “Electronic structure to tungsten and some of its borides, carbides, nitrides, and oxides by x-ray electron spectroscopy”, Inorg. Chem. 15, 236 (1976).
[16] P. Biloen, and G. T. Pott, “X-ray photoelectron spectroscopy study of supported tungsten oxide”, J. Catal. 30, 169 (1973).
[17] I. Kojima, and M. Kurahashi, “Application of asymmetrical Gaussian/Lorentzian mixed function for X-ray photoelectron curve synthesis”, J. Electron Spectrosc. Relat. Phenom. 42, 177 (1987).

References of Chapter 6
[1] Y. Koltypin, S. I. Nikitenko, and A. Gedanken, “The sonochemical preparation of tungsten oxide nanoparticles”, J. Mater. Chem. 12, 1107 (2002).
[2] C. Santato, M. Odziemkowski, M. Ulmann, and J. Augustynski, “Crystallographically oriented mesoporous WO3 films: synthesis, characterization, and applications”, J. Am. Chem. Soc. 123, 10639 (2001).
[3] N. Renard, C. Sella, O. Nemraoui, M. Maaza, Y. Sampeur, and J. Lafait, “Preparation, characterization and properties of sputtered electrochromic and thermochromic devices”, Surf. Coat. Technol. 98, 1477 (1998).
[4] Y. Zhao, Z. C. Feng, and Y. Liang, “Pulsed laser deposition of WO3-base film for NO2 gas sensor application”, Sens. Actuators B 66, 171 (2000).
[5] H. Meixner, J. Gerblinger, U. Lampe, and M. Fleischer, “Thin-film gas sensors based on semiconducting metal oxides”, Sens. Actuators B 23, 119 (1995).
[6] J. L. Solis, S. Saukko, L. Kish, C. G. Granqvist, and V. Lantto, “Semiconductor gas sensors based on nanostructured tungsten oxide”, Thin Solid Films 391, 255 (2001).
[7] L. G. Teoh, I. M. Hung, J. Shieh, W. H. Lai, and M. H. Hon, “High sensitivity semiconductor NO2 gas sensor based on mesoporous WO3 thin film”, Electrochem. Solid State Lett. 6, G108 (2003).
[8] Y. S. Kim, S. C. Ha, K. Kim, H. Yang, S. Y. Choi, Y. T. Kim, J. T. Park, C. H. Lee, J. Choi, J. Paek, and K. Lee, “Room-temperature semiconductor gas sensor based on nonstoichiometric tungsten oxide nanorod film”, Appl. Phys. Lett. 86, 213105 (2005).
[9] Y. Li, Y. Bando, and D. Golberg, “Quasi-aligned single-crystalline W18O49 nanotubes and nanowires”, Adv. Mater. 15, 1294 (2003).
[10] K. Liu, D. T. Foord, and L. Scipioni, “Easy growth of undoped and doped tungsten oxide nanowires with high purity and orientation”, Nanotechnology 16, 10 (2005).
[11] G. Gu, B. Zheng, W. Q. Han, S. Roth, and J. Liu, “Tungsten oxide nanowires on tungsten substrates”, Nano Lett. 2, 849 (2002).
[12] Y. Z. Jin, Y. Q. Zhu, R. L. D. Whitby, N. Yao, R. Ma, P. C. P. Watts, H. W. Kroto, and D. R. M. Walton, “Simple approaches to quality large-scale tungsten oxide nanoneedles”, J. Phys. Chem. B 108, 15572 (2004).
[13] M. H. Cho, S. A. Park, K. D. Yang, I. W. Lyo, K. Jeong, S. K. Kang, D. H. Ko, K. W. Kwon, J. H. Ku, S. Y. Choi, and H. J. Shin, “Evolution of tungsten-oxide whiskers synthesized by a rapid thermal-annealing treatment”, J. Vac. Sci. Technol. B 22, 1084 (2004).
[14] J. Pfeifer, E. Badaljan, P. Tekula-Buxbaum, T. Kovacs, O. Geszti, A. L. Toth, and H. J. Lunk, “Growth and morphology of W18O49 crystals produced by microwave decomposition of ammonium paratungstate”, J. Cryst. Growth 169, 727 (1996).
[15] J. Liu, Y. Zhao, and Z. Zhang, “Low-temperature synthesis of large-scale arrays of aligned tungsten oxide nanorods”, J. Phys.: Condens. Matter 15, L453 (2003).
[16] H. G. Choi, Y. H. Jung, and D. K. Kim, “Solvothermal synthesis of tungsten oxide nanorod/nanowire/nanosheet”, J. Am. Ceram. Soc. 88, 1684 (2005).
[17] X. L. Li, J. F. Liu, and Y. D. Li, “Large-scale synthesis of tungsten oxide nanowires with high aspect ratio”, Inorg. Chem. 42, 921 (2003).
[18] Y. G. Shen, Y. W. Mai, Q. C. Zhang, D. R. McKenzie, W. D. McFall, and W. E. McBride, “Residual stress, microstructure, and structure of tungsten thin films deposited by magnetron sputtering”, J. Appl. Phys. 87, 177 (2000).
[19] T. H. Fleisch, and G. J. Mains, “An XPS study of the UV reduction and photochromism of MoO3 and WO3”, J. Chem. Phys. 76, 780 (1982).
[20] D. Mueller, and A. Shih, “A synchrotron radiation study of BaO films on W(001) and their interaction with H2O, CO2, and O2”, J. Vac. Sci. Technol. A 6, 1067 (1988).
[21] I. Kojima, and M. Kurahashi, “Application of asymmetrical Gaussian/Lorentzian mixed function for X-ray photoelectron curve synthesis”, J. Electron Spectrosc. Relat. Phenom. 42, 177 (1987).
[22] L. Salvati, L. E. Makovsky, J. M. Stencel, F. R. Brown, and D. M. Hercules, “Surface spectroscopic study of tungsten-alumina catalysts using x-ray photoelectron, ion scattering, and Raman spectroscopes”, J. Phys. Chem. 85, 3700 (1981).
[23] S. J. Wang, C. H. Chen, R. M. Ko, Y. C. Kuo, K. M. Uang, T. M. Chen, and B. W. Liou, “Preparation of tungsten oxide nanowires from sputter-deposited WCx films using an annealing/oxidation process”, Appl. Phys. Lett. 86, 263103 (2005).

References of Chapter 7
[1] V. V. S. Rana, J. C. Jr. Desko, A. S. Manocha, K.-H. Lee, and A. K. Sinha, “Selective tungsten plugs on silicon for advanced CMOS devices”, IEDM 33, 862 (1987).
[2] S. J. Wang, H. Y. Tsai, S. C. Sun, and M. H. Shiao, “Thermal stability of sputtered tungsten carbide as diffusion barrier for copper metallization”, J. Electrochem. Soc. 148, G500 (2001).
[3] J. L. Solis, S. Saukko, L. B. Kish, C. G. Granqvist, and V. Lantto, “Nanocrystalline tungsten oxide thick-films with high sensitivity to H2S at room temperature”, Sens. Actuators B 77, 316 (2001).
[4] M. Penza, M. A. Tagliente, L. Mirenghi, C. Gerardi, C. Martucci, and G. Cassano, “Tungsten trioxide (WO3) sputtered thin films for a NOx gas sensor”, Sens. Actuators B 50, 9 (1998).
[5] M. Di. Giulio, D. Manno, G. Micocci, A. Serra, and A. Tepore, “Gas-sensing properties of sputtered thin films of tungsten oxide”, J. Phys. D: Appl. Phys. 30, 3211 (1997).
[6] S. J. Wang, C. H. Chen, S. C. Chang, K. M. Uang, C. P. Juan, and H. C. Cheng, “Growth and characterization of tungsten carbide nanowires by thermal annealing of sputter-deposited WCx films”, Appl. Phys. Lett. 85, 2358 (2004).
[7] S. J. Wang, C. H. Chen, S. C. Chang, C. H. Wong, K. M. Uang, T. M. Chen, R. M. Ko, and B. W. Liou, “On the thermal annealing conditions for self-synthesis of tungsten carbide nanowires from WCx films”, Nanotechnology, 16, 273 (2005).
[8] S. J. Wang, C. H. Chen, R. M. Ko, Yi. C. Kuo, C. H. Wong, C. H. Wu, K. M. Uang, T. M. Chen, and B. W. Liou, “Preparation of tungsten oxide nanowires from sputter-deposited WCx films using an annealing/oxidation process”, Appl. Phys. Lett. 86, 263103 (2005).
[9] Y. H. Lee, C. H. Choi, Y. T. Jang, E. K. Kim, and B. K. Ju, “Tungsten nanowires and their field electron emission properties”, Appl. Phys. Lett. 81, 745 (2002).
[10] Y. Li, Y. Bando, and D. Golberg, “Quasi-aligned single-crystalline W18O49 nanotubes and nanowires”, Adv. Mater. 15, 1294 (2003).
[11] J. Zhou, L. Gong, S. Z. Deng, J. Chen, J. C. She, N. S. Xu, R. Yang, and Z. L. Wang, “Growth and field-emission property of tungsten oxide nanotip arrays”, Appl. Phys. Lett. 87, 223108 (2005).
[12] J. Liu, Z. Zhang, Y. Zhao, X. Su, S. Liu, and E. Wang, “Tuning the field-emission properties of tungsten oxide nanorods”, Small 1, 310 (2005).
[13] J. Pfeifer, E. Badaljan, P. Tekula-Buxbaum, T. Kovacs, O. Geszti, A. L. Toth, and H. J. Lunk, “Growth and morphology of W18O49 crystals produced by microwave decomposition of ammonium paratungstate” J. Cryst. Growth 169, 727 (1996).
[14] Y. Z. Jin, Y. Q. Zhu, R. L. D. Whitby, N. Yao, R. Ma, P. C. P. Watts, H. W. Kroto, and D. R. M. Walton, “Simple approaches to quality large-scale tungsten oxide nanoneedles”, J. Phys. Chem. B 108, 15572 (2004).
[15] Y. G. Shen, Y. W. Mai, Q. C. Zhang, D. R. McKenzie, D. McFallW, and E. McBrideW, “Residual stress, microstructure, and structure of tungsten thin films deposited by magnetron sputtering” J. Appl. Phys. 87, 177 (2000).
[16] C. H. Chen, S. J. Wang, R. M. Ko, Y. C. Kuo, K. M. Uang, T. M. Chen, B. W. Liou, and H. Y. Tsai, “The influence of oxygen content in the sputtering gas on the self-synthesis of tungsten oxide nanowires on sputter-deposited tungsten films”, Nanotechnology 17, 217 (2006).
[17] R. M. Ko, S. J. Wang, C. H. Chen, W. C. Tsai, Y. C. Kuo, C. L. Chang, and Z. F. Wen, “The influence of carbon content on material and field emission properties of nanowires self-synthesized from sputter-deposited WCx films”, submitted to SSDM 2006.

References of Chapter 8
[1] Y. H. Lee, C. H. Choi, Y. T. Jang, E. K. Kim, B. K. Ju, N. K. Min, and J. H. Ahn, “Tungsten nanowires and their field electron emission properties”, Appl. Phys. Lett. 745, 81 (2002).