The study is triethylamine to ZnO thin film in crystal modification Adviser : David.T.W.Lin Reporter : Chi-Hung Tsai   Institute of Mechatronic System Engineering, National University of Tainan 我這篇主要在講的是氧化鋅性質的研究在表面聲波元件上 談聲波特性，表面聲波與體聲波簡介，表面聲波與體聲波最大不同 Date : 2013/12/07

Outline 1. Introduction 2. Motivation and Purpose 3. Experimental Methods 4. Results and Discussions 5. Conclusions 6. References

ZnO material Properties N-type semiconductor material. It has piezoelectric properties at (002) direction. High resistance and high transmittance It can through doping to improve the film properties . 六方纖鋅礦結構 應用 太陽能電池、LED燈、二極體、光電感測器 ---- 透光率80%以上 氧化鋅現在是具有潛能的材料 目前可取代ITO AZO 導電薄膜

Device applications SAW filters SAW sensors Video Communication Touch panel In these few years, as a results of sensor growing mature. SAW device has become Important issue. 感測器成熟發展，表面聲波成為重要的議題，早期表面聲波用於國防及軍事系統，由於現代科技發達。因此也應用到感測器、濾波器、通訊系統和觸控面板…等 This is common applications such as filters, sensors, video communication, touch panel.

SAW Substrate 1. Wave propagation is stable. Flexible substrate Advantage Disadvantage 1. Applies to non-planar occasions. 2. Lightweight and Thin Difficult to manufacture. Rigid substrate 1. Wave propagation is stable. 2. Manufacturing process can be done under high temperature. The limitation of usage. 目前表面聲波元件，由於體積小重量輕朝向高頻化發展 本身元件的波傳特性佔有很大的影響，基板動機，做個比較，說到本文動機

Motivation and Purpose 1.Finding the best crystalline property of ZnO film by different speeds 2. Adding stabilizer into solution in future works 藉由探討氧化鋅性質對壓電特性的影響，進一步改良表面聲波元件 由於氧化鋅沉積表面還不太理想，我們嘗試未來加入穩定劑改良壓電薄膜表面，使之後鍍電擊較為容易

Piezoelectric effect(1/2) Direct piezoelectric effect + - + - + - 壓電效應分成正負壓電效應 壓電材料是因為材料能夠因為正負離子無法平衡，產生電偶極矩的材料 正壓電效應介紹 - +

Piezoelectric effect(2/2) Converse piezoelectric effect + - + - 逆壓電效應介紹 故知道外部作用力能與材料產生晶格共振 + - - +

Deposition methods Molecular beam epitaxy (MBE) Chemical vapor deposition (CVD) 薄膜沉積方法介紹 我們利用SOL GEL Sol-Gel method Sputtering method Electrochemical deposition

Piezoelectric film & Substrate ZnO film PI substrate This is my structure. In the right picture, PI is flexible substrate, and ZnO film is piezoelectric material. In the left picture, It utilizes the solute and solvent mixture to get the solution by heating and stirring. Substrate PI Length 1cm Width Height 0.02mm

Sol-Gel Process 1. Sloution deployment 2. Film deposition 3. Bake 4. Thermal annealing This is our deposition method for experiment, and it called sol-gel method It has to through four steps. Sloution deployment – 主要是先調配出想要的溶液，溶液的濃度比例都會影響薄膜品質，過程中會濾掉不必要的雜質，提高薄膜均勻度   It is mainly deployment of solution composition. It will affect film quality and solution concentration, and it has to go through filtration to clear impurities unnecessary, and enhance film uniformity. Film deposition 製作完溶液之後，利用沉積的方法將溶液沉積在基板上面，沉積介紹， 旋轉塗佈 It is mainly deposition solution on substrate Our experiment uses spin coating to deposition the solution, it is able to cause centrifugal force by speed of rotation and get the uniform distribution on substrate. Bake 沉積完之後利用加熱機烤乾，藉此輝發掉有機溶劑和有機物質，其目的是消除薄膜中的碳鏈 It is mainly liquid film to become solid film by solvent evaporation because it can eliminate carbon chain in film. Thermal annealing 最後再藉由退火過程將薄膜結晶 主要是薄膜結晶且消除薄膜殘留應力 It is mainly the film crystallization and eliminate residual stress. Sol-gel method can get high pure and uniform film in low temperatures. 我們利用熔膠凝膠法沉積氧化鋅，因為熔膠凝膠法可以除了製作簡單之外它可以在低溫下得到純度高的溶液

Experiment In order to get the best crystalline film, we use spin coating to deposit film by different speeds. The part of measurement is analysis by XRD and SEM We can know that the crystalline properties by XRD, and the principle uses angle of incidence and angle of reflection to detect the diffracted electron And we can also know that the surface morphology of atomic by SEM, it uses electron beam to hit the surface of substrate and detect by secondary signal Finally, we can get the better result

Experiment This is my experiment flowchart. In step 1, we deploy ZnO solution and doing surface modification by oxygen plasma. It can easy to make solution attaches on substrate. In step 2, we deposit ZnO film by spin coating, after that, we heat the film by hot plate, and repeat the previous action until the layers what you want. Finally, we must make the film changes crystallization by anneal process. In step 3, we get the film property by XRD and SEM.

Results and Discussion XRD pattern This is XRD results of experiment. X-axis is the angle of reflection. Y-axis is the signal intensity. We can get the best crystalline speed at 400 rpm from different speeds. And we see the (002) direction for ZnO film, and the angle is about 34.4 degrees. It is dependents on crystal quality of ZnO film by the signal direction, and the intensity of (002) direction is much higher than the other speeds.   (002)

Results and Discussion SEM image This shows atomic surface morphology of ZnO film by SEM image. We can see the grain is largest at the speed of 400RPM, and it also has better coverage from SEM image. Therefore, it has best crystalline property for ZnO film.  

Conclusion The better crystalline property of ZnO film can be obtain in low speeds. The better result of coating speed is 400 RPM from fixed parameters such as 1mole concentration、Annealing temperature of 250 degrees and 3 deposition layers . The better coverage of the ZnO atomic can be observed by SEM This shows the conclusion. We summarize the following two points.   These experiment parameters are 400 RPM (Molar concentration Annealing temperature、Deposition layers and so on). The better coverage of the ZnO atomics can be observed by SEM 覆蓋性越高 結晶越完整

References Lord Rayleigh, ‘‘On Waves Propagated along the Plane Surface of an Elastic Solid’’, Proc, London Math, Soc, Vol.17, pp.4-11, 1885. White R.M., Voltmer F.W., ‘‘Direct piezoelectric coupling to surface elastic waves’’, Appl. Phys. Lett., Vol.7, Issue 12, pp.314–316., 1965. Curie, P.J., ‘‘Developpement par pression de l’electricite polaire dans des crystaux hemiedriques a faces inclines’’, Compt. rend., Vol.91,NO. 294-295, pp.383-387., 1880. Hsueh, T.-J., Chen, Y.-W., Changa, S.-J., Wang, S.-F., Hsuc, C.-L., Lin, Y.-R., Lin, T.-S and Chene, I.C., ‘‘ZnO nanowire-based CO sensors prepared on patterned ZnO:Ga/SiO2/Si templates. ’’, Sensors and Actuators B: Chemical, Vol.125, Issue 2, pp.498-503., 2007. Chougule, M.A., Sen, S and Patil, V.B., ‘‘Fabrication of nanostructured ZnO thin film V sensor for NO2 monitoring’’, Ceramics International, Vol.38, No.4, pp.2685-2692., 2012. Gao, W., Li, Z.,‘‘ZnO thin films produced by magnetron sputtering. ’’, Ceramics International., Vol.30, Issue 7, pp.1155-1159., 2004.

References Bensmaine, S., Brizoual, L. L., Elmazria, O., Fundenberger, J.J., Belmahi, and M., Benyoucef, B., ‘‘SAW devices based on ZnO inclined c-axis on diamond.’’, Diamond and Related Materials, Vol.17, No. 7-10, pp.1420-1423., 2008. Yang, P.-F., Wen, H.-C., Jian, S.-R., Lai, Y.-S., Wu, Sean and Chen, R.-S., ‘‘Characteristics of ZnO thin films prepared by radio frequency magnetron sputtering.’’, Microelectronics Reliability, Vol.48, No. 3, pp.389-394., 2008. Shih, W.-C., Wang, T.-L and Pen, Y.-K., ‘‘Enhancement of characteristics of ZnO thin film surface acoustic wave device on glass substrate by introducing an alumina film interlayer. ’’, Applied Surface Science, Vol. 258, No.14, pp.5424-5428., 2012. Hwang, K.-S., Kang, B.-A., Jeong, J.-H., Jeon, Y.-S., and Kim, B.-H., ‘‘Spin coating-pyrolysis derived highly c-axis-oriented ZnO layers pre-fired at various temperatures. ’’, Current Applied Physics, Vol.7, Issue 4, pp.421-425., 2007. Kakati, N., Jee, S.H., Su, H.K., Jun, Y.O and Young, S.Y., ‘‘Thickness dependency of sol-gel derived ZnO thin films on gas sensing behaviors. ’’, Thin Solid Films, Vol.519, No. 1, pp.494-498., 2010.

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