Abstract
Currently, it is challenging to develop new catalysts for semiconductor nanowires (NWs) growth in a complementary-metal-oxide-semiconductor (CMOS) compatible manner via a vapor-liquid-solid (VLS) mechanism. In this study, chemically synthesized Cu2O nano cubes are adopted as the catalyst for single crystalline β-Ga2O3 NWs growth in chemical vapor deposition. The growth temperature is optimized to be 750 to 800 °C. The NW diameter is controlled by tuning the sizes of Cu2O cubes in the 20 to 100 nm range with a bandgap of ~4.85 eV as measured by ultraviolet-visible absorption spectroscopy. More importantly, the catalyst tip is found to be Cu5As2, which is distinguished from those Au-catalyzed Au-Ga alloys. After a comprehensive phase diagram investigation, the β-Ga2O3 NWs are proposed to be grown by the ternary phase of Cu-As-Ga diffusing Ga into the growth frontier of the NW, where Ga react with residual oxygen to form the NWs. Afterward, Ga diminishes after growth since Ga would be the smallest component in the ternary alloy. All these results show the importance of the catalyst choice for CMOS compatible NW growth and also the potency of the ternary phase catalyst growth mode in other semiconductor NWs synthesis.
Highlights
In recent years, Ga2 O3 nanowires (NWs) with a wide bandage of ~4.9 eV have attracted greater attention because of the unique structural, electronic, mechanical, and optical properties, such as having a Debye length comparable to the small size and tuned band gap based on size restriction, which is applicable to various electronic and optical nano-devices [1,2,3,4,5,6,7,8]
Ga2 O3 NWs catalyzed by Cu2 O
This can be interpreted by limited gallium source vaporized and deposited because of low sectional SEM images illustrating the length of the NWs
Summary
Ga2 O3 nanowires (NWs) with a wide bandage of ~4.9 eV have attracted greater attention because of the unique structural, electronic, mechanical, and optical properties, such as having a Debye length comparable to the small size and tuned band gap based on size restriction, which is applicable to various electronic and optical nano-devices [1,2,3,4,5,6,7,8]. It is necessary to adopt substitute metal catalysts for the complementary-metal-oxide-semiconductor (CMOS) compatibility [21,27,28]. To solve this problem, self-catalyzed growth methods and CMOS compatible metal catalyst induced growth technologies that have been developed for the semiconductor NWs growth [15,16,28]. Complicated substrate treatment would be desired in order to obtain a diameter uniform NW growth because NW diameters would vary greatly if there is no foreign catalyst in the self-catalyzed growth [15]. Thermally annealing the metal films, which are physically deposited by thermal and/or e-beam evaporation that mainly form the catalyst particles. Vincent et al fabricated Si NWs using copper-based catalysts and finding the original seed layer that is absolutely oxidized to Cu2 O at the optimum oxygen pressure by comparing different oxygen pressures for producing straight
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