ZnSe nanorings and its cathodoluminescence

Abstract

In this paper, we report free-stand wurtzite phase growth, the system was cooled gradually to room temperature.ZnSe nanorings and zinc blende phase nanowires fabricated on A bright yellow colored product was obtained on the Si Au coated Si substrates through the thermal evaporation of substrate after the growth.pristine ZnSe powders. The Ring-or wire-like nanstructures can be achieved in a controllable manner by using different reactor B. Characterization ofZnSe nanostructures pressures during growth, while all the other conditions remain T the same. To our knowledge, the wurtzite phase ZnSe rings have The as-synthesis samples were characterized by transmission not been reported to date. The growth mechanism of the electron microscopy (TEM, JEOL 2010), field emission nanorings has been discussed and the cathodoluminescence of the scanning electron microscopy (FE-SEM, LEO 1530) equipped nanorings has been described.with an energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD, Rigaku RU-300 with CuKa radiation), and Keywords-wurtzite phase ZnSe, metastable phase ZnSe, cathodoluminescence (CL) system attached to SEM. nanorings, nanowires, growth mechanism, cathodoluminescence III. RESULTS AND DISCUSSION I. INTRODUCTION Zinc Selenide (ZnSe) is an important wide-band-gap JI-JVI A. ZnSe nanorings and nanowires semiconductor for applications in short-wavelength Figure 1 shows the SEM image of an as-synthesis sample optoelectronic devices such as blue laser diodes, light-emitting grown at 0.2 torr in low magnification. It can be seen that a diodes (LEDs), photodetectors [1-3], and window materials in large amount of ring-like structures were grown. The inset the field of photovoltaics15. ZnSe can also be combined with shows the higher magnification SEM image of a typical ring. other II-VI semiconductors such as ZnO taking the advantage It can be observed that the ring is formed by a close-loop belt. of carrier transfer between two binary II-VI semiconductorsThe rings usually have diameters of about few microns. The with different energy levels for device applications [4,5]. typical thickness of the rings is about 50-100 nm. We find that Recently, ZnSe nanowires [6], nanobelts [7] and ZnSe the formation of the rings is sensitive to the growth pressure.nanorods on in-situ synthesized ZnSe grains [8] have been When the growth is held at a pressure higher than or equal to reported. However, most of the reports on ZnSe nanostructures 10 torr, zinc-blende structured nanowires (see figure 2) are were focused on the zinc-blende structure, only a few on its grown instead of rings. The zinc-blende structure is confirmed wurtzite counterpart yet without detailed explanation [7,9].by XRD as shown as in the inset of figure 2. EDX analyses of Here, we show the controlled growth of wurtzite ZnSe the rings have been conducted to study the composition of the nanorings by simple thermal evaporation through changing the rings and a typical spectrum is shown in figure 3. The results reactor pressure. The formation of the wu...