| 摘要 | GaN, GaP (Ga(N,P))是重要的III-V族半导体材料，被广泛应用在发光二极管、光电探测器、场效应晶体管、太阳能电池等光电器件上。由于准一维纳米材料具有独特的量子尺寸效应，因此准一维Ga(N,P)纳米材料有望用于构建高性能纳米光电器件。但由于目前对准一维Ga(N,P)纳米材料的生长机理还不十分清楚，因此，准一维Ga(N,P)纳米材料尚不能控制合成，材料的结构-性能关系亟待进一步揭示。本文围绕准一维Ga(N,P)纳米材料的制备与表征展开工作，取得了以下初步成果：
采用化学气相输运和沉积的制备方法，以Ga2O3粉末和红P为原料，水蒸汽为生长促进剂，在900-1000℃和无催化剂的条件下，制备出P掺杂的三角形GaN纳米管。该GaN纳米管长度达几十个微米，其等边三角形截面的边长为0.5-1μm，厚度为几十个纳米，边与边之间的结合不紧密，其轴向生长方向为[0001]，三个侧面的晶面指数为{11-20}，P元素的掺杂量在4.2-6.5at%之间。场发射性能研究表明：P掺杂的三角形GaN纳米管的开启电场仅为2.9V/μm，比P掺杂的GaN纳米线（5.9V/μm）降低了约50%，比不掺杂的GaN纳米线（8.5V/μm）降低了约66%。场发射性能提高的原因主要源于三个方面：P元素的有效掺杂、粗糙的表面形貌和奇异的三角形管状结构。
采用化学气相输运和沉积的制备方法，在过量Ga反应物浓度和920-980℃的条件下，制备出GaP纳米链。GaP纳米链由纳米线串联纳米球组成，其中，纳米线直径为10-100nm；纳米球直径为100nm-10μm。GaP纳米链为单晶闪锌矿结构，生长方向为[111]。可能的生长机制为：首先生长出直径均匀的GaP纳米线；然后Ga液滴吸附在GaP纳米线表面，同时进行润湿过程与化学反应过程；最后形成GaP纳米链。
在化学气相输运和沉积的过程中，采用两步生长法，在950℃的温度下，依次以H2和NH3为反应气体制备出GaPO4-GaN同轴纳米线。XRD、SEM、HRTEM、 SAED和EDS等研究表明：GaPO4-GaN同轴纳米线的平均直径仅为15nm，其芯部为正交晶系的GaPO4晶体，外壳为纤锌矿结构的GaN晶体。
制备得到的GaN纳米管，GaP纳米链和GaPO4-GaN同轴纳米线等准一维Ga(N,P)纳米材料可能具有独特的场发射、电子传输行为和光学特性，因而具有重要的科学研究价值并可望在纳米光电器件等领域得到应用。 |
| 其他摘要 | As important III-V semiconductor materials, GaN/GaP (Ga(N,P)), have been widely applied for light-emitting diodes, photodetector, field effect transistor, solar cell and other optoelectronic devices. Compared with the bulk materials, quasi-one-dimensional (1D) nanomaterials own some unique properties, such as enhanced luminescence properties and excellent field-emission performances, because of their high aspect ratio and size effect. Therefore, 1D Ga(N,P) have great protential to develop as high-performance optoelectronic nano-devices. However, till now the growth mechanism of 1D Ga(N,P) nanostructures is still not clear; their growth lack controllability and the relationship between structure and property should be expored. In this study, the synthesis and characterization of 1D Ga(N,P) nanostructures have been investigated and the corresponding results are as following:
P-doped GaN nanotubes with triangular cross-section were synthesized by a catalyst-free chemical vapor transport and deposition method by using Ga2O3 and red phosphorus as raw materials, H2O vapor as reaction promoter at 900-1000℃. The length of P-doped triangular GaN nanotubes is tens of micrometers. The shape of cross section is equilateral triangle, and the side is 0.5-1μm in width and several tens of nanometers in thickness; and the joint between the sides is not close. The growth direction of the GaN nanotubes is along [0001]; and crystal plane index of three side surface is {11-20}; and the content of P element varies from 4.2 to 6.5at%. Field-emission (FE) measurement shows that the turn-on field of P-doped triangular GaN nanotube is ~2.9V/μm, which decreased by ~50% than that of P-doped GaN nanowires and reduced by ~66% than that of the undoped GaN nanowires. The factors which contribute to the improvement of FE property are the effective P doping, rough surface, and the unique triangular tube structures.
GaP nanochains were synthesized by a chemical vapor transport and deposition method using excessive Ga sources at 920-980℃. The GaP nanochains are composed of nanowires and nanoballs. The diameter of nanowires is in the range of 10-100nm, while the nanballs have a diameter of 100nm to 10μm. The GaP nanochain is single-crystalline zinc blende structure and the growth direction is along [111]. The probable growth mechanism is as following: firstly the smooth GaP nanowires formed; then the Ga droplet adsorbed on the surface of GaP nanowires to happen wetting process and chemical reaction process at the same time; last there formed GaP nanochain.
GaPO4-GaN coaxial nanowires were synthesized by a two-step chemical vapor deposition method using H2 and NH3 as reactant gas in turn at 950℃. XRD, SEM, HRTEM, SAED, and EDS have been carried out to study the as-synthesized product and reveal that the average diameter of GaPO4-GaN coaxial nanowires is ~15nm, and the core is orthorhombic GaPO4 cryatal and the outer shell is hexagonal GaN crystal.
The as-synthesized GaN nanotube, GaP nanochain and GaPO4-GaN coaxial nanowire may have unique FE properties, electron transport behaviors and optical properties, so they have great research value and are expect to be applied in optoelectronics field. |
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