Thermal Evaporation Synthesis and Optical Properties of ZnS Microbelts on Si and Si/SiO 2 Substrates V.N. NGUYEN, 1 N.T. KHOI, 1 and D.H. NGUYEN 1,2 1.—Advanced Institute for Science and Technology (AIST), Hanoi University of Science and Technology (HUST), 01 Dai Co Viet, Hanoi, Vietnam. 2.—e-mail: hung.nguyenduy@hust.edu.vn In this study, we report on the differences in optical properties of zinc sulfide (ZnS) microbelts grown on Si and Si/SiO 2 substrates by a thermal evaporation method. Our investigation suggests that the composition and luminescence of the microbelts are dependent on the growth substrate. Field emission scan- ning electron microscopy images show the formation of nanoparticles with a diameter of 300–400 nm on ZnS microbelts grown on Si substrate. In addition, energy dispersive x-ray spectroscopy analysis combined with x-ray diffraction and Raman measurements reveal the existence of Si on these microbelts which may bond with O to form SiO 2 or amorphous silica. In contrast, no Si presents on the microbelts grown on Si/SiO 2 substrate. Moreover, photolu- minescence measurement at 300 K shows a narrow emission peak in the near- ultraviolet region from microbelts grown on Si/SiO 2 substrate but a broad emission band with multi-peaks from microbelts grown on Si substrate. The origin of the luminescence distinction between microbelts is discussed in terms of the differences in the growth substrates and compositions. Key words: ZnS microbelts, thermal evaporation, Si substrate, photoluminescence INTRODUCTION Wide-band-gap semiconductors have attracted considerable attention because of their possible applications in optoelectronic devices, energy con- version devices, and transparent conducting elec- trodes, thanks to their excellent electronic, optical, and thermal properties. 1,2 While III–V compound semiconductors have already found many applica- tions in optoelectronics devices such as light-emit- ting diodes, solar cells, and displays, II–VI compounds are still under development and have been actively studied in recent years. 3,4 ZnS is a direct wide-band-gap II–VI semiconductor with a high refractive index and significant transmittance in the visible range of the electromagnetic spectrum with band gaps of 3.72 eV and 3.77 eV for cubic zincblende and hexagonal wurtzite crystal struc- tures, respectively. ZnS has recently garnered much interest because of the nanostructures which have a large surface–volume ratio. 5 Various nanostruc- tures of ZnS, including nanowires, nanoribbons, nanocombs, nanorods, and nanobelts, have been synthesized by different methods such as chemical vapor deposition, 6 molecular-beam epitaxy, 7 metal– organic chemical vapor deposition, 8 hydrothermal methods, 9 pulsed laser deposition, 10 and thermal evaporation. 11–14 Among those available techniques, the thermal evaporation and vapor-phase transport methods have been extensively used because well- formed nanostructures with high crystalline quality can be grown in a simple, cost-effective, and scalable way. 14–16 The thermal evaporation method seems to be favored for high-temperature growth in most cases. 11–14 For practical applications, ZnS nanos- tructures have been usually grown on Si and Si/ SiO 2 substrates because they are relatively inex- pensive and appropriate for use in Si-based photonic devices. 8,11,12,15,16 In fact, ZnS nanostructures grown on these different substrates have signifi- cantly different morphologies. 17 However, ZnS is easily oxidized into ZnO as a nanostructure. To (Received October 1, 2016; accepted March 28, 2017) Journal of ELECTRONIC MATERIALS DOI: 10.1007/s11664-017-5489-6 Ó 2017 The Minerals, Metals & Materials Society