Tunable and Predetermined Bandgap Emissions in Alloyed ZnSxSe1–x Nanowires

Abstract

1D nanostructures such as nanowires, nanorods, nanobelts, and nanotubes have become the focus of intensive research owing to their novel physical properties and applications in the fabrication of nanoscale devices. They are expected to be as interconnects and functional units in electronic, optoelectronic, and other devices with nanoscale dimensions. Wide-gap II-VI semiconductors can be efficient emitters in the blue to ultraviolet spectral region, and excitons in these compounds are much more stable than those in the conventional III-V semiconductors that are widely used in optoelectronic field. In the past decade, considerable efforts were made to prepare 1D II-VI semiconductors and to investigate their optoelectronic properties. Among these researches, only the fixed bandgap emissions of binary II-VI semiconductors were studied; however, obtaining tunable and predetermined optoelectronic properties is significant for the practical applications of these 1D II-VI semiconductors. Therefore, it is important and desired to achieve tunable and predetermined bandgap emissions in 1D II-VI semiconductors. Alloying of binary II-VI semiconductors is an important method to obtain tunable bandgap emissions through composition modulation. Scheme 1 illustrates that Eg(ABxC1–x) (the energy gap of the alloyed ABxC1–x) can be continuously tuned from Eg(AB) (the energy gap of the binary compound AB) to Eg(AC) (the energy gap of the binary compound AC) as the composition x decreases. This method has been widely used in thin films or nanocrystals in order to obtain tunable optical properties; however, there are few reports on the fabrication of alloyed 1D nanostructures. Recently, alloyed ZnxCd1–xS nanoribbons and CdSxSe1–x nanobelts were obtained by means of a laser ablation-assisted CVD method and a simple one-step physical evaporation process, respectively. Furthermore, the previous studies show that the variation of Eg(ABxC1–x) can be represented as a quadratic function of composition x, Eg(ABxC1–x) = xEg(AB) + (1 – x)Eg(AC) – x(1 – x)b, where b is the bowing parameter. [12]