奈米金屬點有很高的表體比例，很適合來觀察與氣體反應的現象。由於與氣體反應需在具有氣體的環境下進行，利用無法利用電子束當作偵測方式。而螢光光譜或是拉曼光譜則是因為單層或是物理吸附等條件無法提供對應的訊號。利用反射二次諧波來分析奈米金屬點與氣體反應時電偶極矩的改變可以解析出細微的動態變化。在奈米金屬點開始氧化前，需經歷物理吸附與化學吸附的過程，而這些反應與溫度與壓力息息相關，且會影響氧化層的建立。這一個工作是建立在本實驗室具有特色的受局限奈米鋅顆粒在Si(111)的樣本製作與即時量測方式，透過反射二次諧波與 UV光的照射來分析物理吸附行為，與後續化學吸附的產生。由於溫度增加有助於化學吸附但降低物理吸附的量，兩者之間的權衡下，有效氧化層的形成速率並非與溫度正相關。這一個工作報導在不同溫度與壓力下，物理吸附與化學吸附的變遷，並詮釋了氧化層建立前的過程。

Collective Zn dots were deposited on Si(111) substrates by magnetron RF sputtering, which condition was combined with a RF power of 100 W and negative substrate bias of −500 V, and kept the ratio of hydrogen to argon at approximately 18% in the working chamber with the pressures of 1×10−2 torr. H2 reduces ZnO and removes SiO2 in the strategic RF sputtering, which results enhancement on the diffusion of Zn adatoms. Besides, the substrate temperature was kept at 250 °C to achieve the reduction of ZnO by H2 and the surface diffusion of Zn adatoms. Zn dots are formed from liquid to solid phases after cooling. The size distribution of the dots is strongly dependent on the growth conditions and growth time. The oxidization of Zn dots was performed in the sputtering chamber without expose to air to avoid the humidity.The net dipole contribution from the Zn dots was analyzed via RSHG experiments, which the setup and operation method of these experiments are described in. Synchrotron XRD was performed at the 17B1 stations of the National Synchrotron Radiation Research Center in Taiwan.

[1] L. Yuan, Y. Wang, R. Mema and G. Zhou, “Driving force and growth mechanism for spontaneous oxide nanowire formation during the thermal oxidation of metals,” Acta Materialia 59 (2011) 2491–2500
[2] C. M. Wang, D. R. Baer, L. E. Thomas, J. E. Amonette, J. Antony, Y. Qiang and G. Duscher, “Void formation during early stages of passivation: Initial oxidation of iron nanoparticles at room temperature,” J. Appl. Phys. 98 (2005) 094308
[3] R. Nakamura, J.-G. Lee, D. Tokozakura, H. Mori and H. Nakajima, “Formation of hollow ZnO through low-temperature oxidation of Zn nanoparticles,” Materials Letters 61 (2007) 1060–1063
[4] A. K. Mahapatra, U. M. Bhatta and T. Som, “Oxidation mechanism in metal
nanoclusters: Zn nanoclusters to ZnO hollow nanoclusters,” J. Phys. D: Appl. Phys. 45(2012) 415303
[5] H. Vázquez, Y. J. Dappe, J. Ortega, and F. Flores, “Energy level alignment at metal/organic semiconductor interfaces:“Pillow” effect, induced density of interface states, and charge neutrality level,” J. Chem. Phys. 126 (2007) 144703
[6] H. Moormann, D. Kohl and G. Heland, “Work function and band bending on clean cleaved zinc oxide surfaces,” Surface Science 80 (1979) 261-264
[7] N. D. Orf, L. D. Baikie, O. Shapira and Y. Fink, “Work function engineering in low-temperature metals,” Applied Physics Letters 94(2009)113504
[8] I. Langmuir, “The constitution and fundamental properties of solids and liquids, ” constitution of solids and liquids (1916)
[9] A. Rothschild, Y. Komem, “Numerical computation of chemisorption isotherms for
device modeling of semiconductor gas sensors,” Sensors and Actuators B 93 (2003) 362–369
[10] J. John, IV. Perry, L. Stephanie, T. McGoldrick, S. T. Meek, J. A. Greathouse, M. Haranczyk and M. D. Allendorf. “Noble Gas Adsorption in Metal−Organic Frameworks Containing Open Metal Sites,” The Journal of Physical Chemistry C(2014)
[11] D. Heskeft, L. E. Urbach, K. J. Song, E. W. Plummer and H.L. Dai, “Oxygen and pyridine on Ag(110) studied by second harmonic generation: coexistence of two phases within monolayer pyridine coverage, ” Science 197 (1988) 225-238
[12] J. Tao and A. M. Rappe, “Physical Adsorption: Theory of van der Waals Interactions between Particles and Clean Surfaces,” Physical Review Letters 112 (2014) 106101
[13] L. Czepirski, M. R. Balys, E. K. Czepirska, “Some generalization of Langmuir adsorption isotherm,” Internet Journal of Chemistry (2000)3 14
[14] S. S. Nalimova, A. A. Ryabko, A. I. Maximov and V. A. Moshnikov, “Light-activation of gas sensitive layers based on zinc oxide nanowires, ” Journal of Physics: Conference Series 1697 (2020) 012128
[15] C. B. Jacobs, A. B. Maksov, E. S. Muckley, L. Collins, M. M. Samani1, A. Ievlev, C. M. Rouleau, J.W. Moon, D. E. Graham, B. G. Sumpter and I. N. Ivanov, “UV-activated ZnO films on a flexible substrate for room temperature O2 and H2O sensing,” Scientific Reports (2017) 7: 6053 DOI:10.1038/s41598-017-05265-5
[16] S.W. Fan, A. K. Srivastava and Vi. P. Dravid, “UV-activated room-temperature gas sensing mechanism of polycrystalline ZnO,” Appl. Phys. Lett. 95(2009)142106
[17] S. Brahma, C.W. Yang, C.H. Wu, F.M. Chang, T.J. Wu, C.S. Huang, K.Y. Lo, “The optical response of ZnO nanorods induced by oxygen chemisorption and desorption, ” Sensors and Actuators B 259 (2018) 900–907
[18] N. D. Lang and W. Kohn, “Theory of metal surfaces: Work Function, ” Physical Review B vol. 3 num. 4 (1971)
[19] V. Lantto and P. Romppainen, “Electricl studies on yhe reactions of CO with different oxygen species on SnO2 Surfaces,” Surface Science 192 (1987) 243-264
[20] L. S. Mende and J. L. M. Driscoll, “ZnO-nanostructures, defects and devices,” materials today vol. 10, num. 5 (2007).
[21] C.S. Prajapati, D. Visser, S. Anand and N. Bhat, “Honeycomb type ZnO nanostructures for sensitive and selective CO detection,” Sensors and Actuators B: Chemical vol. 252(2017) 764–772
[22] C.Y. Liu, B.P. Zhang, N.T. Binh, Y. Segawa, “Second harmonic generation in ZnO thin films fabricated by metalorganic chemical vapor deposition,” Optics Communications vol. 237 (2004) 65–70
[23] M. Niskanen, M. Kuisma, O. Cramariuc, V. Golovanov, T. I. Hukka, N. Tkachenko and T. T. Rantala, “Porphyrin adsorbed on the(1010) surface of the wurtzite structure of ZnO-conformation induced effects on the electron transfer characteristics,” Phys. Chem. Chem. Phys, 15,(2013) 17408-17418
[24] 莊達人 著，VLSI 製造技術，高立圖書股份有限公司，P146-160 (1995)
[25] 陳海峰，薛莹洁，表面技術 56-63 (2016)
[26] 陳建人，真空技術與應用，國家實驗研究院儀器科技研究中心出版 (2008)
[27] P.J. Kelly, R.D. Arnell, “Magnetron sputtering: a review of recent developments and applications,” Vacuum 56 159-172 (2000)
[28] 泓威科技，真空鍍膜設備
[29] B. J. Huang, L.C. Kao, S. Brahma, Y.E. Jeng, S. J. Chiu, C. S. Ku and K.Y. Lo, “Epitaxial Zn quantum dots coherently grown on Si(111): grown mechanism, nonlinear optical and chemical states analyses,” J. Phys. D: Appl. Phys. 50 (2017)
[30] C.C. Liu, J.H. Huang, C.S. Ku, S.J. Chiu, J. Ghatak, S. Brahma, C.W. Liu, C.P. Liu, and K.Y. Lo, “Crystal Orientation Dynamics of Collective Zn dots before Preferential Nucleation” Scientific Reports 5, 12533 (2015)
[31] C. Schwab, G. Meister, J. Woll, A. Gerlach, A. Goldmann,“Experimental intensity analysis of second harmonic generation at the Cu(110) surface,” Surface Science 457 273–284 (2000)
[32] D. A. Koos, V. L. Shannon and G. L. Richmond, “Surface dipole and electric quadrupole contributions to the anisotropic second harmonic generation from noble metal surfaces,” Physical review b volume 47, number 8 4730-4734 (1992)
[33] Luo, Y. R. (2007) Comprehensive Handbook of Chemical Bond Energies, Boca Raton, FL, CRC Press.
[34] Kelin, j. K. (1998) Laser Engineering ,Prentic-Hall
[35] Robert W. Boyd (2008) Nonlinear Optics 3ed.
[36] N. Kawamoto, M. Fujita, T. Taatsumi and Y. Horikoshi, “Growth of ZnO on Si Substrate by Plasma-Assisted Molecular Beam Epitaxy,” Jpn. J. Appl. Phys. Vol. 42 7209–7212(2003)
[37] M. Frigo and S.G. Johnson, “ FFTW: An adaptive software architecture for the FFT,” IEEE、3、1381-1384(1998).
[38]. F. S.S. Chien, C.R. Wang, Y.L. Chan, H.L. Lin, M.H. Chen, R.J. Wu, “Fast-response ozone sensor with ZnO nanorods grown by chemical vapor deposition,” Sensors and Actuators B 144 120–125 (2010)