製備與鑑定新穎一維奈米結構：氮化鎵與二氧化矽

Abstract

藉由VLS與SLS機制，我們成功地合成出具有特殊方向性的刷狀氮化鎵奈米晶體、非晶相二氧化矽奈米線，及二氧化矽包覆銦之一維奈米結構。 結合二次化學氣相沉積與氮化處理，我們製備出同質奈米接合產物--刷狀氮化鎵奈米結構其主軸奈米線直徑約70~150奈米，輻向奈米棒直徑約20~70奈米，依特殊對稱性排列於主軸上。進一步晶體結構分析得知，刷狀奈米晶體為單晶wurtzite氮化鎵結構，輻向奈米棒沿主軸之[01-1]方向磊晶而成，導致輻向奈米棒依特殊對稱方式排列。本實驗可應用於製備其他同質或異質奈米接合結構，如InN on GaN等。 此外，藉由低共熔點之鎵作為催化劑，並結合SLS機制，我們推測可於較低溫度下製備出二氧化矽奈米線。分析結果顯示，產物為非晶相二氧化矽奈米線，其直徑約10~40奈米並具有均一長度，垂直基板成長並排列成薄膜狀。實驗結果不如預期可降低奈米線成長溫度，然而此方法卻可推廣至其他低熔點金屬，催化成長高排列性之奈米線。 二氧化矽包覆銦之一維奈米結構的發現，是在成長磷化銦奈米線之偶然情況下被合成出來的。近一步鑑定得知，非晶相之二氧化矽管壁包覆著間斷的結晶性銦奈米棒，其管壁外徑約300~600奈米、內徑約200~500奈米。銦為低熔點高沸點、高膨脹係數之金屬，這使得二氧化矽包覆銦之一維奈米結構可應用於奈米尺寸下的溫度量測。 利用簡單高溫化學氣相沉積設備，我們製備出特殊一維奈米結構，關於其性質將有更深入的研究探討，而其潛在應用價值也是未來研究的重點。

A simple route for the synthesis of unique 1D nanostructures, including brush-like gallium nitride nanostructure, oriented amorphous silicon nanowires and In@SiO2 nanocables, was developed on the basis of VLS and SLS mechanisms. GaN nanobrushes with geometric symmetries were fabricated via a two-step growth process. Morphological studies indicated the diameters of trunk nanowires and branch nanorods ranged from 70 to 150nm and 20 to 70nm respectively. According to crystal structure analyses, most nanobrushes exhibited single crystalline structure indexed to h-GaN and branch nanorods were epitaxially grown on trunk nanowires along direction of [01-1]. Using low-melting-point metal as catalyst, the practicability of silica nanowires grown at lower temperature was expected. Amorphous silica nanowires with diameters of 10~40nm and length of up to ~50m were formed via SLS mechanism catalyzed by molten Ga metal. Aligned nanowires with uniform length were arranged to thin film. Growth of nanowires occurred at 900℃ in spite of expect at lower temperature. However, the SLS method could be generalized to other low-melting metals, such as In, Bi and Sn, to grow aligned various nanowires. In@SiO2 nanocables were discovered accidentally as we researched in InP nanowires growth. Structural characterization revealed that nanocables composed of discontinuous crystalline In core with diameters of 200~500nm and amorphous silica shell with diameter from 300~600nm. In@SiO2 nanocables may be applied to nanoscale thermometer due to high expansion coefficient of In metal. Unique 1D nanostructures described above are expected to potential application on optoelectronics, NEMS and biochemistry.