随著全球智慧化，物聯網技術的快速發展，以智能材料(熱電、壓電、記憶合金、導電石墨…)製成的感應產品已经廣泛應用於工業和人們的生活當中。壓電氮化铝（AlN）薄膜，具有優良的壓電性能，化學與熱穩定性亦佳又硬度強，可處於較險惡的環境下，且其具有高傳導性及高電阻性，是目前製備各種感測器、傳感器、驅動器、諧振器以及濾波器等的最佳原材料。同時，具有良好導電性的氮化鈦，其在擇優結晶方向(111)可以與氮化鋁(002)銜接，故當少量鈦原子以合成氮化鈦的環境下摻入其中時，並不會影響奈米柱形貌。此外，其除了可以更增進機械性能與壓電系数，還可以有效地利用可見光在光催化的應用上，卻不會顯著改變其它原具優勢的属性，這無疑將進一步提升感應器件的性能。
本研究中，利用AlN和TiN複合奈米柱成分比例調控合成摻雜鈦(Ti)的壓電氮化铝（AlN）固溶體之薄膜材料於摻氟氧化錫玻璃基板，再設計最佳實驗參數以控制其複合材料奈米柱形貌與摻鈦濃度，並透過XRD，SEM，PL，XPS，UV-vis， I-V 特徵圖，及光催化效應來研究其光觸媒及壓電相關性質，從中證實此材料性能增強程度，最後再針對應用端進行研究。

Wurtzite structure AlN have been greatly used as heat dissipation components, wear resistance, and corrosion protective coatings. AlN has a high Curie temperature of approximately 1150 °C, enabling the sustainability of its excellent piezoelectric response at high temperatures. However, its low piezoelectric coefficients d33 (approximately 5.5 pC/N), poor conductivity, and wide band gap (approximately 6.2 eV) greatly limited the wide range of applications.
Although Ti doped AlN enabled the enhancement of the piezoelectricity of AlN and the formation energy was low, their mutual solubility was limited because of their extremely high hardness. In this study, a desirable combinatorial AlN-TiN nanocolumn composite composition spread was fabricated using reactive sputtering to systemically study the formation of TixAl1-xN and its effective coupling with AlN and TiN in the system. The physical, optical, electrical, piezophotocatalytic, and photoelectrochemical properties were comprehensively studied. The highlights of this study included:

1. TixAl1-xN solid solution evolution from #1 to #6 was observed across the composition spreads (Sample #104) through the XRD analysis.
2. XPS depth profiling was employed to determine the Al/Ti ratio variations and the interfaces across Sample #104. The layering structures were then deduced.
3. The pure AlN exhibited extremely high PL intensity because of the defect resulted recombination centers. The pure TiN exhibited much weaker peaks associated with the band-to-band transition and defect-induced recombination. The PL intensities were substantially reduced from #1 to #6 on Sample #104, compared with those of AlN, and the exhibited spectra were similar to that of pure AlN, indicating the predominant AlN in the system.
4. The optical properties (absorption edges) of pure AlN, TiN, and Sample #104 were studied using UV-vis spectroscopy.
5. The valence band positions of various samples were studied using UPS measurements.
6. The energy band diagrams of pure AlN, TiN, and Sample #104 were systemically derived on the basis of the PL, UV-vis, and UPS results.
7. No piezotronic and piezophototronic properties were observed for TiN through I-V measurements because of its excellent conductivity. Weak piezotronic and piezophototronic features were observed for AlN. However, #1 on Sample #104 exhibited much stronger effects. The Schottky contact behavior was also quantitatively studied, which greatly supported the piezo-related measurement results.
8. The photodegradation measurement revealed that #1 on Sample #104 exhibited the best piezophotodegradation capability with the coefficient of approximately 7.5E-3/min because of the intimate coupling of minor TiN, TixAl1-xN, and AlN. A cycling test verified its stability and reusability, indicating a great potential photocatalyst for environmental sustainability-related applications.
9. #1 and #6 on Sample #104 exhibited super PEC performance, In addition, approximately 755% and 233% enhancement were observed for #1 and #6, respectively, when stress was additional applied, indicating excellent PPEC properties of #1.

[1] Y. Saito, H. Takao, T. Tani, T. Nonoyama, K. Takatori, T. Homma, T. Nagaya, M. Nakamura, " Lead-free piezoceramics, " Nature 432, 84–87 (2004)
[2] H. Sun, Y. Zhang, X. Liu, S. Guo, Y. Liu, W. Chen, " The effect of Mn/Nb doping on dielectric and ferroelectric properties of PZT thin films prepared by sol–gel process," Journal of sol-gel science and technology 74 2, 378-386 (2015)
[3] J. Chang, M. Dommer, C. Chang, L. Lin, "Piezoelectric nanofibers for energy scavenging applications," Nano Energy 1, 356-371 (2012)
[4] X. Chen, S. Guo, J. Li, G. T. Zhang, M. Lu, and Y. Shi, "Flexible piezoelectric nanofiber composite membranes as high performance acoustic emission sensors," Sensors and Actuators A: Physical 199, 372-378 (2013)
[5] P. K. Panda and B. Sahoo, "PZT to Lead Free Piezo Ceramics: A Review," Ferroelectrics 474, 128-143 (2015)
[6] H. Nagata, M. Yoshida, Y. Makiuchi, T. Takenaka, “Large Piezoelectric Constant and High Curie Temperature of Lead-Free Piezoelectric Ceramic Ternary System Based on Bismuth Sodium Titanate-Bismuth Potassium Titanate-Barium Titanate near the Morphotropic Phase Boundary,” Japanese Journal of Applied Physics 42, 7401–7403 (2003)
[7] A. Sasaki, T. Chiba, Y. Mamiya, E. Otsuki, “Dielectric and Piezoelectric Properties of (Bi0.5Na0.5)TiO3–(Bi0.5K0.5)TiO3 Systems,” Japanese Journal of Applied Physics 38, 5564–5567 (1999)
[8] X. Wang, J. Wu, D. Xiao, J. Zhu, X. Cheng, T. Zheng, “Giant Piezoelectricity in Potassium–Sodium Niobate Lead-Free Ceramics,” Journal of the American Chemical Society 136 7, 2905-2910 (2014)
[9] J. P. Praveen, T. Karthik, A.R. James, E. Chandrakala, S. Asthana, D. Das, “Effect of poling process on piezoelectric properties of sol–gel derived BZT–BCT ceramics,” Journal of the European Ceramic Society 35 6, 1785-1798 (2015)
[10] H. Yang, C. Zhou, X. Liu, Q. Zhou, G. Chen, W. Li, H. Wang, “Piezoelectric properties and temperature stabilities of Mn- and Cu-modified BiFeO3-BaTiO3 high temperature ceramics,” journal of the European ceramic society 33 6, 1177-1183 (2013)
[11] K. Cho, D. H. Kim, Y. H. Kim, J. Nah, H. K. Kim, “Li-doped Cu2O/ZnO heterojunction for flexible and semi-transparent piezoelectric nanogenerators,” Ceramics International 43 2, 2279-2287 (2017)
[12] Z. L. Wang, J. H. Song, “Piezoelectric nanogenerators based on zinc oxide nanowire arrays,” Science 312 5771, 242-246 (2006)
[13] Y. Fu, Y. Nie, Y. Zhao, P. Wang, L. Xing, Y. Zhang, X. Xue, " Detecting Liquefied Petroleum Gas (LPG) at Room Temperature Using ZnSnO3/ZnO Nanowire Piezo-Nanogenerator as Self-Powered Gas Sensor," American Chemical Society 7 19, 10482–10490 (2015)
[14] Q. Li, J. Wei, J. Cheng, J. Chen, "High temperature dielectric, ferroelectric and piezoelectric properties of Mn-modified BiFeO3-BaTiO3 lead-free ceramics," Journal of Materials Science 52 1, 229-237 (2017)
[15] D. Damjanovic, “Ferroelectric, dielectric and piezoelectric properties of ferroelectric thin films and ceramics,” Reports on Progress in Physics 61 9, 1267-1324 (1998)
[16] G. H. Haertling., “Ferroelectric ceramics: History and technology,” Journal of the American ceramic society 82 4, 797-818 (1999)
[17] C. R. Bowen, H. A. Kim, P. M. Weaver, and S. Dunn, “Piezoelectric and ferroelectric materials and structures for energy harvesting applications,” energy & environmental science 7 1, 25-44 (2014)
[18] V. Chang, H. Rojas, and J. Jorge, "Piezoelectric and thermoelectric response of cuprous oxide, Cu2O," Sensors and Actuators A: Physical 37-38, 375-378 (1993)
[19] E. S. Nour, A. Bondarevs, P. Huss, M. Sandberg, S. Gong, M. Willander, O. Nur, "Low-Frequency Self-Powered Footstep Sensor Based on ZnO Nanowires on Paper Substrate," Nanoscale Res Lett 11, 156 (2016)
[20] X. Li, M. Chen, R. Yu, T. Zhang, D. Song, R. Liang, Q. Zhang, S. Cheng, L. Dong, A. Pan, Z. L. Wang, J. Zhu, and C. Pan, "Enhancing Light Emission of ZnO-Nanofilm/Si-Micropillar Heterostructure Arrays by Piezo-Phototronic Effect," Advanced Materials 27 30, 4447-4453 (2015)
[21] M. K. Lo, S. Y. Lee, and K. S. Chang, "Study of ZnSnO3-Nanowire Piezophotocatalyst Using Two-Step Hydrothermal Synthesis," Journal of Physical Chemistry C 119 9, 5218-5224 (2015)
[22] Sang-Moo Park, Tomoaki Ikegami, Kenji Ebihara, “Effects of substrate temperature on the properties of Ga-doped ZnO by pulsed laser deposition,” Thin Solid Films 513, 90–94 (2006)
[23] S. K. Si, S. K. Karan, S. Paria, A. Maitra, A. K. Das, R. Bera, A. Bera, L. Halder, B. B. Khatua, " A strategy to develop an efficient piezoelectric nanogenerator through ZTO assistedg-phase nucleation of PVDF in ZTO/PVDF nanocompositefor harvesting bio-mechanical energy and energy storage application," Materials Chemistry and Physics 213, 525-537 (2018)
[24] J. M. Wu, C. Y. Chen, Y. Zhang, K. H. Chen, Y. Yang, Y. Hu, J. H. He, Z. L. Wang, "Ultrahigh sensitive piezotronic strain sensors based on a ZnSnO3 nanowire/microwire," American Chemical Society Nano 6, 4369-4374 (2012)
[25] B. E. Foutz, O. Ambacher, M. J. Murphy, V. Tilak, L. F. Eastman, "Polarization Induced Charge at Heterojunctions of the III–V Nitrides and Their Alloys," Physica Status Solidi (B) 216, 415-418 (1999)
[26] N. Gogneau, N. Jamond, P. Chretien, F. Houze, E. Lefeuvre, M. Tchernycheva, "From single III-nitride nanowires to piezoelectric generators: New route for powering nomad electronics," Semiconductor Science and Technology 31 10, 103009 (2016)
[27] Th. Pavloudis, J. Kioseoglou, Th. Karakostas, Ph. Komninou, "Ordered structures in III-Nitride ternary alloys," Computational Materials Science 118, 22-31 (2016)
[28] R. Agrawal, H. D. Espinosa, "Giant piezoelectric size effects in zinc oxide and gallium nitride nanowires. A first principles investigation," Nano Lett 11, 786-790 (2011)
[29] M. Tomar, V. Gupta, A. Mansingh, and K. Sreenivas, “Temperature stability of c -axis oriented LiNbO3/SiO2/Si thin film layered structures,” Journal of Physics D: Applied Physics 34 15, 2267–2273 (2001)
[30] A. Barker, S. Crowther, and D. Rees, “Room-temperature RF magnetron sputtered ZnO for electromechanical devices,” Sensors and Actuators A: Physical 58 3, 229–235 (1997)
[31] O. J. Gregory, A. B. Slot, P. S. Amons, E. E. Crisman, “High temperature strain gages based on reactively sputtered AlNx thin films,” Surface and Coatings Technology 88 1–3, 79–89 (1997)
[32] X. H. Xu, H. S. Wu, C. J. Zhang, Z. H. Jin, “Morphological properties of AlN piezoelectric thin films deposited by DC reactive magnetron sputtering,” Thin Solid Films 388, 62-67 (2001)
[33] S. R. M. Levnishtein, “Properties of Advanced Semiconductor Materials,” New York: John Wiley & Sons (2001)
[34] J. J. B. EunHyun, O. MinSuk, H. JunHee, J. JinWoo, “Industrial applications of cathodic-arc and RF/DC magnetron plasma,” IEEE International Conference on Plasma Science, 163 (1995)
[35] Y. Hu, Y. Zhang, Y. Chang, “Optimizing the Power Output of a ZnO Photocell by Piezopotential,” American Chemical Society Nano 4 7, 4220-4224 (2010)
[36] X. Wang, X. Lu, B. Liu, D. Chen, Y. Tong, G. Shen, “Flexible Energy-Storage Devices: Design Consideration and Recent Progress,” advanced material 26 28, 4763-4782 (2014)
[37] A.P.M. Michel, J. Kapit, “Deep Ultraviolet Light Emitting Diode (LED)-Based Sensing of Sulfur Dioxide,” applied spectroscopy 71 5, 996-1003 (2017)
[38] R. Maeda, J. J. Tsaur, S. H. Lee, M. Ichiki, “Piezoelectric microactuator devices,” journal of electroceramics 12 (1-2), 89-100 (2004)
[39] D. Kumar, J. Antifakos, M. G. Blamire, Z. H. Barber, “High curie temperatures in ferromagnetic Cr-doped AlN thin films,” applied physics letters 84 24, 5004-5006 (2004).
[40] K. Tonisch, V. Cimalla, Ch. Foerster, H. Romanus, O. Ambacher, D. Dontsov, “Piezoelectric properties of polycrystalline AlN thin films for MEMS application”, Sensors and Actuators A 132 2, 658-663(2006).
[41] M. Akiyama, K. Umeda, A. Honda, T. Nagase “Influence of scandium concentration on power generation figure of merit of scandium aluminum nitride thin films,” applied physics letters 102 2, 021915 (2013)
[42] F. Tasnádi, B. Alling, C. Höglund, G. Wingqvist, J. Birch, L. Hultman, and I. A. Abrikosov, “Origin of the Anomalous Piezoelectric Response in Wurtzite ScxAl1−xN Alloys,” Physical review letters 104 13, 137601 (2010)
[43] Y. Iwazaki, T. Yokoyama, T. Nishihara, and M. Ueda, “Highly enhanced piezoelectric property of co-doped AlN,” Applied Physics Express 8 6, 061501 (2015)
[44] H. Sugisawa, H. Kitaura, K. Ueda, K. Kimura, M. Ishida, Y. Ochi, A. Kishikawa, S. Ogawa, T. T. Yamamoto, “Corrosion resistance and mechanical properties of titanium nitride plating on orthodontic wires.,” Dental Materials Journal 37 2, 286-292 (2018)
[45] M. N. Solovan, V. V. Brus, E. V. Maistruk, P. D. Maryanchuk, “Electrical and optical properties of TiN thin films,” Neorganicheskie Materialy 50 1, 46–51 (2014)
[46] R. Singh, M. Boettcher, I. Panchenko, C. Fiedler, A. Schwarz, J. Wolf, “Fabrication and characterization of precise integrated titanium nitride thin film resistors for 2.5D interposer,” International Spring Seminar on Electronics Technology (ISSE) 978 1, 5386-0582 (2017)
[47] V. A. Ageev, A. K. Vershina, “Effect of synthesis conditions protective and decorative titanium nitride coatings on their optical and color parameters,” Journal of Applied Spectroscopy 65 1, 88-96 (1998)
[48] M. Marlo, V. Milman, “Density functional study of bulk and surface properties of titanium nitride using different exchange correlation functionals,” physical review B 62 4, 2899-2907 (2000)
[49] C. Muratore, J.J. Hu, A.A. Voevodin, “Adaptive nanocomposite coatings with a titanium nitride diffusion barrier mask for high-temperature tribological applications,” Thin Solid Films 515 7–8, 3638–3643 (2007)
[50] Z. L. Wang, "Piezotronic and Piezophototronic Effects," The Journal of Physical Chemistry Letters 1, 1388-1393 (2010).
[51] M. B. Starr and X. Wang, "Fundamental analysis of piezocatalysis process on the surfaces of strained piezoelectric materials," Scientific reports 3, 2160 (2013)
[52] Z. Guo, H. Li, L. Zhou, D. Zhao, Y. Wu, Z. Zhang, W. Zhang, C. Li, J. Yao, "Large-scale horizontally aligned ZnO microrod arrays with controlled orientation, periodic distribution as building blocks for chip-in piezo-phototronic LEDs," Small 11 4, 438-445 (2015).
[53] L. Zhu, L. Wang, F. Xue, L. Chen, J. Fu, X. Feng, T. Li, Z. L. Wang, "Piezo-Phototronic Effect Enhanced Flexible Solar Cells Based on n-ZnO/p-SnS Core-Shell Nanowire Array," Advanced Science (Weinh) 4, 1600185 (2017).
[54] W. Deng, L. Jin, B. Zhang, Y. Chen, L. Mao, H. Zhang, W. Yang, "A flexible field-limited ordered ZnO nanorod-based self-powered tactile sensor array for electronic skin," Nanoscale 8, 16302-16306 (2016)
[55] X. Guo, Y. Fu, D. Hong, B. Yu, H. He, Q. Wang, L. Xing, X. Xue, "High-efficiency sono-solar-induced degradation of organic dye by the piezophototronic/photocatalytic coupling effect of FeS/ZnO nanoarrays," Nanotechnology 27, 375704 (2016)
[56] X. Liu, X. Yang, G. Gao, Z. Yang, H. Liu, Q. Li, Z. Lou, G. Shen, L. Liao, C. Pan, Z. L. Wang, "Enhancing Photoresponsivity of Self-Aligned MoS2 Field-Effect Transistors by Piezo-Phototronic Effect from GaN Nanowires," American Chemical Society Nano 10 8, 7451-7457 (2016).
[57] J. Zhou, P. Fei, Y. Gu, W. Mai, Y. Gao, R. Yang, G. Bao, Z. L. Wang, "Piezoelectric-potential-controlled polarity-reversible Schottky diodes and switches of ZnO wires," Nano Letters 8 11, 3973-3977 (2008)
[58] F. Bernardini, V. Fiorentini, D. Vanderbilt, “Spontaneous polarization and piezoelectric constants of III-V nitrides,” physical review B 56 16, 10024-10027 (1997)
[59] Z. L. Wang, “ZnO nanowire and nanobelt platform for nanotechnology,” 64 3-4, 33-71(2006)
[60] Y. Taniyasu, M. Kasu, T. Makimoto, “An aluminium nitride light-emitting diode with a wavelength of 210 nanometres,” nature 441 7091, 325-328 (2006)
[61] Y. Liu, Y. Zhang, Q. Yang, S. M. Niu, and Z. L. Wang, "Fundamental theories of piezotronics and piezo-phototronics," Nano Energy 14, 257-275 (2015).
[62] Z. L. Wang, "Nanopiezotronics," Advanced Materials 19, 889-892 (2007).
[63] S. Bai, J. Jiang, Q. Zhang, Y. Xiong, " Steering charge kinetics in photocatalysis: intersection of materials syntheses, characterization techniques and theoretical simulations," The Royal Society of Chemistry 44, 2893--2939 (2015)
[64] Z. L. Wang, "Progress in piezotronics and piezo-phototronics," Adv Mater 24, 4632-4646 (2012)
[65] M. Dawber., K.M. Rabe, J.F. Scott, “Physics of thin-film ferroelectric oxides,” reviews of modern physics 77 4, 1083-1130 (2005)
[66] A. Fujishima, K. Honda, “One and Two-dimensional Structure of Alpha-Helix and Beta-sheet Forms of poly(Γ-Alanine) shown by Specific Heat Measurements at Low Temperature (1.5-20K),” Nature 238, 37-38(1972)
[67] A. Fujishima, X. Zhang, D. A. Tryk, “TiO2 photocatalysis and related surface phenomena,” Surface Science Reports 63, 515-582 (2008)
[68] K. Nakata, A. Fujishima, “TiO2 photocatalysis: Design and applications,” Journal of Photochemistry and Photobiology C: photochemistry Review 13, 169-189 (2012)
[69] X. Bai, L. Wang, R. Zong, Y. Lv, Y. Sun, Y. Zhu, “performance Enhancement of ZnO Photocatalyst via Synergic Effect of Surface Oxygen Defect and Graphene Hybridiazation,” Langmuir 29, 3097-3105 (2013)
[70] G. S. Li, D. Q. Zhang, and J. C. Yu, “A New Visible- Light Photocatalyst: CdS Quantum Dots Embedded Mesoporous TiO2,” Environmental Science & Technology 43, 7079-7085 (2009)
[71] E. Tükenmez, “Tungsten Oxide Nanopowders and Its Photocatalyic Activity under Visible Light Irradiation,” Bachelor thesis, Umea Univerity, Sweden (2013)
[72] M. B. Starr, J. Shi, and X. Wang, "Piezopotential-Driven Redox Reactions at the Surface of Piezoelectric Materials," Angewandte Chemie International Edition 51, 5962-5966 (2012)
[73] K.-S. Hong, H. Xu, H. Konishi, and X. Li, "Direct Water Splitting Through Vibrating Piezoelectric Microfibers in Water," The Journal of Physical Chemistry Letters 1, 997-1002 (2010)
[74] K. S. Hong, H. Xu, H. Konishi, and X. Li, "Piezoelectrochemical Effect: A New Mechanism for Azo Dye Decolorization in Aqueous Solution through Vibrating Piezoelectric Microfibers," The Journal of Physical Chemistry C 116, 13045-13051 (2012)
[75] M. B. Starr, X. Wang, “Fundamental Analysis of Piezocatalysis Process on the Surfaces of Strained Piezoelectric Materials,” Scientific reports 3, 2160 (2013)
[76] H. Li, Y. Sang, S. Chang, X. Huang, Y. Zhang, R. Yang, H. Jiang, H. Liu, and Z. L. Wang, "Enhanced Ferroelectric-Nanocrystal-Based Hybrid Photocatalysis by Ultrasonic-Wave-Generated Piezophototronic Effect," Nano Letters 15, 2372-2379 (2015)
[77] X. Xue, W. Zang, P. Deng, Q. Wang, L. Xing, Y. Zhang, and Z. L. Wang, "Piezo-potential enhanced photocatalytic degradation of organic dye using ZnO nanowires," Nano Energy 13, 414-422 (2015)
[78] L. Wang, S. Liu, Z. Wang, Y. Zhou, Y. Qin, and Z. L. Wang, "Piezotronic Effect Enhanced Photocatalysis in Strained Anisotropic ZnO/TiO2 Nanoplatelets via Thermal Stress," American Chemical Society Nano 10, 2636-2643 (2016)
[79] Z. Chen, H. N. Dinh, and E. Miller, "Photoelectrochemical water splitting: standards, experimental methods, and protocols," 126 (2013).
[80] A. Kudo and Y. Miseki, "Heterogeneous photocatalyst materials for water splitting," Chemical Society Reviews 38, 253-278 (2009)
[81] X. Chen, S. Shen, L. Guo, and S. S. Mao, "Semiconductor-based photocatalytic hydrogen generation," Chemical Reviews 110, 6503–6570 (2010).
[82] J. C. Schuster and J. Bauer, J. “The ternary system titanium-aluminum-nitrogen,” Solid State Chem 53, 260 (1984)
[83] N. Gilles., S. Bourhila, C. Ikeda, Bernard, and R. Madar, “Deposition of (Ti,Al)N thin films by organometallic chemical vapor deposition: thermodynarnic predictions and experimental results,” Surface and Coatings Technology 285, 94–95 (1997)
[84] M. Caron, G. Gagnon, V. Fortin, J. Currie, L. Ouellet, Y. Tremblay, M. Biberger, and R. Renholds, “Early stages of interface reactions between AlN and Ti thin films” Journal of Applied Physics 79, 4468-4473 (1996)
[85] Z. W. He, M. Wang, S. Xu, Y. C. Zhao, Q. Zou, “Reactive formation of AlN precipitates and epitaxial interface in TiN1−x–AlN composites,” Journal of the Ceramic Society of Japan 125 1, 46-49 (2017)
[86] E. M. Nia, N. A. W. A. Zawawi, B. S. M. Singh, “A review of walking energy harvesting using piezoelectric materials,” IOP Conference Series: Materials Science and Engineering 291, conference 1 (2017)
[87] H. A. Sonar, J. Paik, “Soft Pneumatic Actuator Skin with Piezoelectric Sensors for Vibrotactile Feedback,” Frontiers in Robotics and AI 2, 38 (2016)
[88] E. Iborra, J. Capilla, J. Olivares, M. Clement, “Piezoelectric and electroacoustic properties of Ti-doped AlN thin films as a function of Ti content,” IEEE International Ultrasonics Symposium Proceedings 978, 2734-2737 (2012)
[89] V. V. Felmetsger, M. K. Mikhov, “Reactive Sputtering of Highly C-Axis Textured Ti-Doped AlN Thin Films,” IEEE International Ultrasonics Symposium Proceedings 978, 782-785 (2012)