石墨烯僅有原子級的厚度且不佔有體積，比表面能相當高，屬於半導體材料及具有極高的載子遷移率，氣體吸附的電荷轉移靈敏度高，對於製作成元件同時兼具傳輸層與感測層的特殊性質，對於各種分子的吸附具有相當的優勢。
本研究以化學氣相沉積法合成雙層石墨烯，為了增加缺陷對於吸附氣體的響應度提高，經過UV/Ozone處理改質表面，增加含氧官能基幫助捕捉氣體分子，得到氧化石墨烯製成蕭特基元件。另外，也將其做200 ℃低溫氬氣之熱退火處理，得到還原氧化石墨烯，與原石墨烯進行響應度比較，然而由XPS分析得知氧原子比例增加，並無達成還原效果。
量測環境分為乾燥空氣與濕空氣，在乾空氣中經過UVO處理10分鐘，對於50 ppm氨氣的響應度可達14.41 %，比原石墨烯的響應度7.72 %高；而退火後，響應度整體下降，其中UVO 1分鐘與3分鐘的響應度增加，可能是適量的氧摻雜退火後形成蝕刻坑造成。濕空氣下的響應效果，與乾燥空氣相比較差，因為氧官能基對水的吸附性強，從250 ppm高濃度氨氣測量至50 ppm低濃度時，已經吸附大量的水分子，影響對氨氣響應度的表現。在RH 30 %低濕度條件下，經過退火處理的氧化石墨烯，響應效果較佳；而在RH 70 %高濕度條件下，則因為吸附過量水氣，對於50 ppm氨氣已無響應。

Graphene is a two-dimensional monolayer of sp2-bonded carbon atoms. Because of its high specific surface area and excellent charge mobility, graphene can be used for gas sensors.
In this work, bi-layer graphene is grown by chemical vapor deposition process. To enhance the response of gas sensing, using UV/Ozone treatment was used to modify the surface of graphene to increase defects including active oxygen functional groups and vacancies, which can efficiently act as adsorption sites for detected gas molecules. The ozone treated graphene is similar to graphene oxide (GO). Additionally, the graphene oxide with low-temperature 200°C annealing in argon was expected to become reduce graphene oxide (RGO). Nevertheless, the graphene oxide hasn’t been reduced after annealing. The atomic ratio of carbon to oxygen increases from X-ray photoelectron spectroscopy.
Two kinds of material are fabricated Schottky devices to compare with PG ammonia gas response. The response is about 14.41 % for UVO treated 10 min Schottky device, which is higher than PG of about 7.74 % to 50 ppm NH3 in dry air ambience. After annealing at 200℃ in argon gas, all responses are decreased. However, the responses of UVO treated 1 min and 3 min devices rise. Because of doping appropriate oxygen and annealing, O2 etch pits are formed. In contrast to the dry air environment, the responses are weaker in humidity air. Oxygen functional groups easily interact with H2O. This phenomenon will affect NH3 gas sensing after long time exposure. The performance of annealed graphene oxide is better than without annealed one to 50 ppm concentration in RH 30 %. When the humidity rises to RH 70 %, the device responses to 50 ppm NH3 no longer.

[1] M. Dubois, Z. Zanolli, X. Declerck and J. C. Charlier, "Electronic properties
and quantum transport in Graphene-based nanostructures," The European
Physical Journal B, vol. 72, pp. 1-24, 2009.
[2] K. S. Novoselov, A. K. Geim, S. V. Morozov, D. Jiang, Y. Zhang, S. V.
Dubonos, I. V. Grigorieva and A. A. Firsov, "Electric Field Effect in
Atomically Thin Carbon Films," Science, vol. 306, no. 5696, pp. 666-669,
2004.
[3] L. Gao, W. Ren, H. Xu, L. Jin, Z. Wang, T. Ma, L.P. Ma, Z. Zhang, Q. Fu, L.
M. Peng, X. Bao and H. M. Cheng, "Repeated growth and bubbling transfer
of graphene with millimetre-size single-crystal grains using platinum,"
Nature Communications, vol. 3, p. 699, 2012.
[4] V. Singh, D. Joung, L. Zhai, S. Das, S. I. Khondaker and S. Seal, "Graphene
based materials: Past, present and future," Progress in Materials Science, vol.
56, no. 8, pp. 1178-1271, 2011.
[5] M. Gao, Y. Pan, L. Huang, H. Hu, L. Z. Zhang, H. M. Guo, S. X. Du and H.
J. Gao, "Epitaxial growth and structural property of graphene on Pt(111),"
Applied Physics Letters, vol. 98, no. 3, 2011.
[6] A. T. N’Diaye, S. Bleikamp, P. J. Feibelman and T. Michely, "Twodimensional
Ir cluster lattice on a graphene Moir'e on Ir(111)," Physical
Review Letters, vol. 9792, no. 92, p. 215501, 2006.
[7] M. Wang, E. H. Yang, R. Vajtai,J. Kono and P. M. Ajayan, "Effects of etchants in the transfer of chemical vapor deposited graphene," Journal of
Applied Physics, vol. 123, no. 19, p. 195103, 2018.
[8] P. R. Somani, S.P. Somani and M. Umeno, "Planer nano-graphenes from
camphor by CVD," Chemical Physics Letters, vol. 403, no. 1-3, pp. 56-59,
2006.
[9] X. Li, C. W. Magnuson, A. Venugopal, J. An, J. W. Suk, B. Han, M. Borysiak,
W. Cai, A. Velamakanni, Y. Zhu, L. Fu, E. M. Vogel, E. Voelkl, L. Colombo
and R. S. Ruoff, "Graphene films with large domain size by a two-step
chemical vapor deposition process," Nano Letters, vol. 10, no. 11, pp. 4328-
4334, 2010.
[10] W. Choi, Y. S. Seo, J. Y. Park, K. B. Kim, J. Jung, N. Lee, Y. Seo and S.
Hong, "Effect of Annealing in Ar/H2 Environment on Chemical Vapor
Deposition-Grown Graphene Transferred With Poly (Methyl
Methacrylate)," IEEE Transactions on Nanotechnology, vol. 14, no. 1, pp.
70-74, 2015.
[11] S. Pei and H. M. Cheng, "The reduction of graphene oxide," Carbon, vol. 50,
no. 9, pp. 3210-3228, 2012.
[12] S. Zhao, S. P. Surwade, Z. Li and H. Liu, "Photochemical oxidation of CVDgrown,"
Nanotechnology, vol. 23, p. 6, 2012.
[13] M. G. Chunga, D.H. Kimb, H. M. Leec, T. Kima and J. H. Choia,, "Highly
sensitive NO2 gas sensor based on ozone treated graphene," Sensors and
Actuators B: Chemical, pp. 172-176, 2012.
[14] G. Lee, B. Lee, J. Kim and K. Cho, "Ozone adsorption on graphene: ab initio
study and experimental validation," Journal of Physical Chemistry C, vol. 113, no. 32, p. 14225–14229, 2009.
[15] J. M. Simmons, B. M. Nichols, S. E. Baker, M. S. Marcus, O. M. Castellini,
C.S. Lee, R. J. Hamers and M. A. Eriksson, "Effect of ozone oxidation on
single-walled carbon nanotubes," Journal of Physical Chemistry B, vol. 110,
no. 14, pp. 7113-7118, 2006.
[16] E. X. Zhang, A. K. M. Newaz, B. Wang, C. X. Zhang, D. M. Fleetwood, K.
I. Bolotin R. D. Schrimpf, S. T. Pantelides and M. L. Alles, "Ozone-exposure
and annealing effects on graphene-on-SiO2 transistors," Applied Physics
Letters, vol. 101, p. 121601, 2012.
[17] D. Yanga, A. Velamakannia, G. l.y Bozoklub, S. Parka, M.Stollera, R. D.
Pinera, S. Stankovichc, I. Junga, D. A. Fieldd, C. A. Ventrice and Rodney S.
Ruoffa, "Chemical analysis of graphene oxide films after heat and chemical
treatments by X-ray photoelectron and Micro-Raman spectroscopy,"
Carbon, vol. 47, no. 1, pp. 145-152, 2009.
[18] H. K. Jeong, Y. P. Mei, H. J. Eun, S. K. Jung, J. B. Young and H.Lee,
"Thermal stability of graphite oxide," Chemical Physics Letters, vol. 470,
no. 4-6, pp. 255-258, 2009.
[19] Ganhua Lu, Leonidas E Ocola, Junhong Chen, "Reduced graphene oxide for
room-temperature gas sensors," Nanotechnology, vol. 20, no. 44, pp.
445502-445511, 2009.
[20] X. Wang, D. Li, Q. Zhang, L. Zou, F. Wang , J. Zhou and Z. Zhang, "Study
on the graphene/silicon Schottky diodes by transferring graphene transparent
electrodes on silicon," Thin Solid Films, vol. 592, no. 1, pp. 281-286, 2015.
[21] W. Tian, X. Liu and W. Yu, "Research Progress of Gas Sensor Based on Graphene and Its Derivatives: A Review," Applied Sciences, vol. 8, no. 7, p.
1118, 2018.
[22] O. Leenaerts, B. Partoens and F. M. Peeters, "Adsorption of H2O, NH3, CO,
NO2, and NO on graphene: A first-principles study," Physical Review B, vol.
77, p. 125416, 2008.
[23] S. Basu and P. Bhattacharyya, "Recent developments on graphene and
graphene oxide based solid state gas sensors," Sensors Actuators B
Chemimcal, vol. 173, pp. 1-21, 2012.
[24] B. C. Wood, S. Y. Bhide, D. Dutta, V. S. Kandagal, A. D. Pathak, S. N.
Punnathanam, K. G. Ayappa and S. Narasimhan, "Methane and carbon
dioxide adsorption on edge-functionalized graphene: A comparative DFT
study," The Journal of Chemical Physics, vol. 137, no. 5, p. 054702, 2012.
[25] I. Maity, K. Ghosh and H. Rahaman, "Selectivity Tuning of Graphene Oxide
Based Reliable Gas Sensor Devices by Tailoring the Oxygen Functional
Groups: A DFT Study Based Approach," IEEE Transactions on Device and
Materials Reliability , vol. 17, no. 4, p. 8, 2017.
[26] H. Wu, X. Bu, Minming Deng, G. Chen , G. Zhang, X. Li, X. Wang and W.
Liu, "A Gas Sensing Channel Composited with Pristine and Oxygen Plasma-
Treated Graphene," Sensors, vol. 19, no. 3, p. 625, 2019.
[27] J. T. Robinson, F. K. Perkins, E. S. Snow, Z. Wei, and P. E. Sheehan,
"Reduced Graphene Oxide Molecular Sensors," Nano Letters, p. 3137–3140,
2008.
[28] H. Wu, Q. Li, X. Bu, W. Liu, G. Cao, X. Li and X. Wang, "Gas sensing
performance of graphene-metal contact after thermal annealing," Sensors and Actuators B: Chemical, pp. 408-416, 2019.
[29] P. Graves and D. Gardiner, "Practical raman spectroscopy," Springer, 1989.
[30] Greenspan, Lewis, "Humidity Fixed Points of Binary Saturated Aqueous
Solutions," Phys ics and Chemistry, vol. 81, pp. 89-96, 1977.
[31] 陳加忠 , 賴建洲 , 曹之祖, "電子相對濕度計之性能評估," 中華農業
研究, pp. 71-89, 1991.
[32] H. Sun, D. Chen, Y. Wu, Q. Yuan, L. Guo, D. Dai, Y. Xu, P. Zhao, N. J. and
C.T. Lin, "High quality graphene films with a clean surface prepared by an
UV/ozone assisted transfer process," Journal of Materials Chemistry C, no.
8, p. 5, 2017.
[33] I. Childres, L. A. Jauregui, W. Park, H. Cao and Y. P. Chen, Raman
spectroscopy of graphene and related materials, vol. 1, New developments
in photon and materials research, 2013.
[34] S. Jandhyala, G. Mordi, B. Lee, G. Lee, C. Floresca, P. Cha, J. Ah, R. M.
Wallace, Y. J. Chabal, M. J. Kim, L. Colombo, K. Cho and J. Kim, "Atomic
Layer Deposition of Dielectrics on Graphene Using Reversibly Physisorbed
Ozone," American Chemical Society, vol. 6, no. 3, pp. 2722-2730, 2012.
[35] L. Liu, S. Ryu, M. R. Tomasik, E. Stolyarova, N. Jung, M. S. Hybertsen,| M.
L. Steigerwald, L. E. Brus and G. W. Flynn, "Graphene Oxidation:
Thickness-Dependent Etching and Strong Chemical Doping," Nano Letters,
vol. 8, no. 7, pp. 1956-1970, 2008.
[36] R. R. Nair, P. Blake, A. N. Grigorenko, K. S. Novoselov, T. J. Booth, T.
Stauber, N. M. R. Peres, A. K. Geim, "Fine Structure Constant Defines
Visual Transparency of Graphene," Science , vol. 320, no. 5881, p. 1308, 2008.
[37] J. Yuan, L. P. Ma, S. Pei, J. Du, Y. Su, W. Ren and H. M. Cheng, "Tuning the
Electrical and Optical Properties of Graphene by Ozone Treatment for
Patterning Monolithic Transparent Electrodes," ACS Nano, vol. 7, no. 5, p.
4233–4241, 2013.
[38] B. Ghosh, M. Das, P. Banerjee and S. Das, "Characteristics of metal/p-SnS
Schottky barrier with and without post-deposition annealing," Solid State
Sciences, vol. 11, no. 2, pp. 461-466, 2009.
[39] K. Jiao, X. Wang, Y. Wang and Y. Chen, "Graphene oxide as an effective
interfacial layer for enhanced graphene/silicon solar cell performance,"
Journal of Materials Chemistry C, vol. 2, no. 37, pp. 7697-7988, 2014.
[40] C. Wang, S. Lei, X. Li, S.i Guo, P. Cui, X. Wei, W. Liu and H. Liu, "A
Reduced GO-Graphene Hybrid Gas Sensor for Ultra-Low Concentration
Ammonia Detection," Sensors, vol. 18, no. 9, p. 3147, 2018.
[41] Jeremy T. Robinson, F. Keith Perkins, Eric S. Snow,, "Reduced Graphene
Oxide Molecular," NANO LETTER, vol. 10, pp. 3137-3140, 2008.
[42] C. Huang, A.k Murat, V. Babar and E. Montes̈ , "Adsorption of the Gas
Molecules NH3, NO, NO2, and CO on Borophene," Journal of Physical
Chemistry C, vol. 122, no. 26, pp. 14665-14670, 2018.