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The Application of Aligned Silicon Nanowires Prepared by Electroless Etching to Surface-enhanced Raman Scattering, Field Emission Display, and Solar Cell Fabrication
|Authors: ||Shi-Wei Chen|
|Contributors: ||NTOU:Institute of Optoelectronic Sciences|
silicon nanowires;electroless etching mechanism;field emission;anti-reflectance of solar cell;surface-enhanced Raman scattering
|Issue Date: ||2011-07-04
|Abstract: ||本論文利用無電鍍蝕刻方法製備準直單晶的矽奈米線，改良其製程並運用於太陽能電池抗反射、場發射與表面增強拉曼上。 在製程改進方面，我們發現，在基板表面刻意加上一層適當厚度的二氧化矽，並且在蝕刻的過程中加上超音波振盪器振盪，可使矽奈米線變得緻密且均勻。 在抗反射方面，我們在不同長度的奈米線樣本測量抗反射效果。發現奈米線長約2μm，在可見光的範圍中的抗反射效率平均可達2%以下。該抗反射特性，應與蝕刻過程導致奈米線由空氣層到矽基板之空間平均填充率漸次變化，形成等效漸變折射率有關。 在表面增強拉曼散射應用上，我們利用奈米線的高表面積，蒸鍍銀顆粒在奈米線上，並量測R6G的拉曼訊號。我們發現其拉曼增強訊號可達到約2.5x107倍，證實矽奈米線可作為表面增強拉曼的基板。 在場發射特性的量測中，我們發現奈米線越長場發射的特性越好，長約3.6μm的奈米線可得到最佳的臨界電場約14.3V/µm。此臨界電場，相較於碳奈米管(~2V//µm)仍偏高，推測可能是因為奈米線相互緊鄰，產生屏蔽效應(Screen effect)，我們建議可利用黃光微影製程將奈米線形成陣列，加以改進。|
In the present thesis, the subject of interest is to improve the fabrication process of well-aligned silicon nanowires (SiNWs) made through electroless etching, as well as to applied SiNWs to solar cell anti-reflection, field emission and surface enhanced Raman scattering. We improved the fabrication process of SiNWs by preforming a SiO2 layer on the substrate followed by ultrasonic violating the etching solution including AgNO3 and HF. Apparently better uniformity and less defect density in SiNWs fabricated with the improved process were attained. To investigate the potential application of SiNWs in solar cell, the antireflection properties of SiNWs with different lengths were studied. The result showed that SiNWs with about 2μm in length gave the lowest reflectance (<2% in the broad visible band). The effective graded index between air and silicon substrate could be responsible for the broad band anti-reflection of the SiNWs. To use the SiNWs as a high surface area substrate for surface-enhanced Raman scattering measurement, we deposited Ag particles on the SiNWs and measure the Raman signal from R6G. An Raman enhanced factor of 2.5x107 was attained on Ag coated SiNWs compared to that estimated on a plane silicon substrate without silver, proving the SiNWs an effective substrate for surface enhanced Raman scattering measurement. The field emission properties of the SiNWs were also studied. It was found that SiNWs with longer lengths basically showed better performance in filed emission. For example, SiNWs with a length of 3.6µm, showed the lowest threshold electrical field at 14.3V/µm. However, the threshold filed, compared to that for carbon nanotube (~2V/µm), was still quite high. The high threshold field could be a result of screen effect due to the high density of nanowires getting to close to each other. For further improvement of the threshold filed, fabrication of SiNWs in arrays using lithographic techniques was recommended.
|Appears in Collections:||[光電科學研究所] 博碩士論文|
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