首先，本研究利用一種以相對低成本且高產率的金屬催化無電鍍蝕刻法成功地在p型及n型矽基材上製備大面積且準直排列之矽晶奈米線與多孔性矽晶奈米線，以供為氣體感測量測。實驗中利用部分試片以氧氣電漿或熱氧化將平板矽與矽晶奈米線進行氧化，使其表面形成一層薄氧化層。研究中也藉由SEM、TEM及SAED針對表面形貌、晶體結構及結晶方向進行一系列鑑定與分析。在氣體感測量測中，具有不同形式氧化層之各式矽晶試片皆具有相同氣體感測特性。由實驗結果可發現在室溫下矽晶奈米線感測試片相較於平板矽感測試片具有較佳的感測特性且靈敏度隨偵測濃度增加而增加，此結果可歸因於矽晶奈米線具有高比表面積所致。 此外，由實驗結果亦可發現不同氧化層之矽基材具有相同的氣體感測行為，然而若將表面氧化層移除則所有矽晶試片皆會失去氣體感測能力。不僅如此，經由一系列氣體偵測實驗顯示n型及p型之各式矽晶試片出乎預料的竟皆表現出與傳統p型金屬氧化物半導體相同之氣體感測特性。此異常的結果，推測矽基材的氣體感測行為可能與矽基材本質無直接相關性，反而是矽基材表面的氧化層在氣體感測機制中扮演關鍵的角色。 ;In this study, p-type and n-type (001) Si wafers were used as the starting materials. To fabricate large-area, vertically aligned silicon nanowires (SiNWs) and porous SiNWs on (001) Si substrate, a low-cost and high-throughput method which is based on metal-assisted electroless chemical etching process was adopted. Some of the blank-Si and SiNWs samples were oxidized by oxygen plasma treatments or thermal oxidation to grow a thin oxide layer on the surfaces. The surface morphologies, crystal structures and crystallographic orientations of the different types of SiNWs samples produced here have been systematically investigated by the SEM, TEM images and SAED analyses. For gas sensing experiments, the blank-Si and SiNW samples were exposed to various concentrations of ammonia and oxygen gases at room temperature. The observed results clearly reveal that compared with blank-Si sample, the vertical Si nanowires sample possesses good gas sensing characteristics at room temperature and their sensitivity increasing with increasing gas concentrations. The enhanced gas-sensing properties can be attributed to the high specific surface of the SiNWs samples. It was also found that the Si-based samples with different oxide shells have almost the same gas-sensing performances. However, if the surface oxide shells were removed, the Si-based samples would lose their gas-sensing ability. Furthermore, contrary to expectation, it was surprising to find that both n-type and p-type Si-based samples exhibited the same characteristics gas-sensing as the conventional p-type metal oxide semiconductors. The abnormal results suggest that the gas-sensing behaviors of Si-based samples may not directly relate to the type of Si substrates. The oxide shells of Si-based samples may play crucial role in the gas-sensing mechanism.
