The studies of photothermoelectric effects in porous silicon

[[abstract]]最近幾年來以多孔矽為材料的元件熱烈被討論以及開發，由於其具有特殊的光學、光電、熱、化學等特性，因此多孔矽在很多領域上有廣泛之研究例如生物及化學感測器、氣體感測器、濕度感測器之應用。又因為他具有可調變能隙(modulated energy bandgap)、高電阻係數(high ressitivity)、極大的表面積/體積比(large surface area-to-volume ratio)以及與本體矽相同的單晶結構，這些優點使得它非常適合作為光偵測器。一般來說製作多孔矽的方法概略分成乾式蝕刻、濕式化學蝕刻與電化學蝕刻。電化學蝕刻保有濕式蝕刻的優點，且具有低設備成本、蝕孔異向性高等優點，是目前最常用於研究多孔矽的製程方法。在本論文中，我們利用電化學蝕刻技術來製備多孔矽層，我們以鐵氟龍、O-ring(防溢橡膠墊圈)、白金薄片與銅片當正負電極來自行組裝蝕刻設備，並藉著調整蝕刻時間、蝕刻溶液濃度比例來形成具不同結構的厚層多孔矽，再以掃描式電子顯微鏡(Scanning Electron Microscope SEM)及光激發螢光(Photo-Luminescence, PL)強度去觀察不同條件參數下多孔矽結構的變化，接著再以其為基底在表面鍍上各式圖樣的金電極。最後研究多孔矽結構的變化及其在不同表面鍍金電極樣式下對於光電與熱電特性量測上的影響，來驗證是否可藉由製程控制及表面特性來改變其結構與其光電與熱的特性。本論文也將目前很夯研究於Graphene的光熱電效應(photothermoelectric effects)原理成功的用來解釋表面鍍金電極之多孔矽光電流產生的原因，並於不同蝕刻時間、不同蝕刻溶液濃度、不同金電極的指 叉數目/指叉間距/厚度、不同光源強度的實驗中找出影響光響應的最佳參數與條件。而此實驗探討與研究方針，相信對於後續應用於製作開發最佳條件的光偵測器與熱偵測器應該具有相當大的幫助。[[abstract]]In recent decades, variety of the porous silicon material components was highly discussed ,investigated and intentional developed , and it has unique characteristics of optics, photoelectric, thermal, chemistry … It has been used in different area, for example, in biosensors, chemical sensors, gas sensor,and humidity sensor. Because of porous silicon has such unique characteristics such as modulated energy bandgap ,high resistivity, large surface area-to-volume ratio, and the same single crystal as silicon ,this advantages make it suit to be photodetectors. In general,porous silicon can be made using dry etching, wet etching, and electrochemicaletching, in which electrochemical etching is the most common method to fabricatedirectional pores due to its low-cost and etching anisotropy .In this work , we fabricateporous silicon on silicon wafer using electrochemical etching. We use teflon ,o-ring (rubber washer) , platinum and cooper as anode and cathode to assemble the etching device to form a thick silicon layer with different porous structure by adjusting the etching time, the ratio of the concentration in the etching solution than we use scanning electron microscope (SEM) and fluorescence excitation light (Photo-Luminescence, PL) intensity to observe the variation of the porous silicon structure that make in different condition. Then we use this porous silicon as a substrate and hot coating a layer of gold pattern on it . In the last we investigate the affect on photoelectric and thermoelectric in different porous silicon structure and different surface gold electrode pattern to verify we canchange its structure and its optical and thermal properties by changing it manufacture process and surface properties. This master thesis we also successfully use photothermoelectric effects theory, which is popular research of graphene in recent day, to explain the reason why the porous silicon with the gold electrode pattern can produce the photocurrent and find the optimum parameters and conditions on the optical response in different etching times, different concentrations of the etching solution, different gold electrode fork numbers / fork spacing / gold thickness, different light intensity experiments. In concluded the experiment &findings of this case study, Istrongly believed the porous silicon of its future application by ways of porous silicon optical sensors development will play a great assist enhancement in a new coming era.[[note]]碩