High-gain visible-blind UV photodetectors based on chlorine-doped n-type ZnS nanoribbons with tunable optoelectronic properties† Yongqiang Yu, ab Jiansheng Jie, * a Peng Jiang, a Li Wang, a Chunyan Wu, a Qiang Peng, a Xiwei Zhang, a Zhi Wang, a Chao Xie, a Di Wu b and Yang Jiang * b Received 4th April 2011, Accepted 17th May 2011 DOI: 10.1039/c1jm11408e Efficient n-type doping of ZnS nanoribbons (NRs) were accomplished by using chlorine (Cl) as the dopant via thermal evaporation. An indium tin oxide (ITO) transparent electrode was used to achieve ohmic contact to the ZnS:Cl NRs. The conductivity of the Cl-doped ZnS NRs was significantly improved as compared with the undoped ones and could be tuned to a wide range of 3–4 orders of magnitude by adjusting the Cl doping level. High-performance nano-photodetectors were constructed based on the ZnS:Cl NRs, which show high sensitivity to the UV light while are nearly blind to the visible light. Notably, the ZnS:Cl NR photodetectors have a photoconductive gain as high as 10 7 , which is amongst the highest values obtained for UV nano-photodetectors so far. Our results demonstrate that the n-type ZnS NRs with tunable optoelectronic properties are promising building blocks for nano-optoelectronic devices. 1 Introduction Zinc sulfide (ZnS), an important II–VI compound semi- conductor with a wide direct bandgap of 3.7 eV, has applications in diverse fields such as flat panel displays, 1 light-emitting diodes (LEDs), 2 and injection lasers. 3 Recently, ZnS nanostructures have attracted increasing attention due to their potential application in a new generation of nano-electronics and nano- optoelectronics. 4 Intrinsic or unintentionally doped ZnS nano- structures are highly insulating due to the high crystal quality with little donor/acceptor defects and are thus not suitable for device applications. The ability to control the optoelectronic properties of ZnS nanostructures via doping is essential in order to realize the future applications. Current research on ZnS nanostructures is mainly focused on the material growth and structure and characterization of optical properties. Studies on their transport properties are rare. Although various metal elements including Mn, Cu, Fe, Co, and Eu have been used as dopants to modulate the optical and magnetic properties of ZnS nanostructures, 5–10 reliable and reproducible doping remains a big challenge. Research on n- and p-type doping of ZnS nanostructures is less than critical and still at the very early stage. 11,12 The development of visible-blind, UV photodetectors is of great importance for optoelectronic and environmental appli- cations. ZnS nanostructures are promising materials for high- performance UV photodetectors owing to the wide bandgap in the UV regime, high quantum-efficiency, high crystallinity, and potential advantages in quantum confinement and size effects. Although nanoscale UV photodetectors based on a variety of wide band-gap nanomaterials such as ZnO and GaN nanowires (NWs) have been investigated, 13,14 ZnS nano-photodetectors are rarely studied and reported. 15,16 This situation might be the result of the difficulties in controlling the transport properties of ZnS nanostructures as well as obtaining good contact between the semiconductor and the electrode. Herein, we report on the tuning of the electronic and opto- electronic properties of n-type ZnS nanoribbons (NRs) via chloride (Cl) doping. Cl was selected as the n-type dopant since it has been reported to be an efficient dopant for achieving high levels of n-type doping with less defects in n-ZnS film. 17,18 Excellent ohmic contact can also be achieved by replacing conventional metallic electrodes with transparent, conducting indium tin oxide (ITO) electrodes. Near visible-blind UV nano- photodetectors with extremely high photoconductive gain (10 7 ) were also demonstrated based on the n-type ZnS:Cl NRs. 2 Experimental details 2.1 ZnS:Cl NRs synthesis and characterization ZnS:Cl NRs were synthesized in a horizontal quartz tube furnace by using a thermal co-evaporation method. 9 0.3 g ZnS power (99.99%, Aldrich) was first loaded into an alumina boat and then a School of Electronic Science and Applied Physics, Hefei University of Technology, Hefei, Anhui, 230009, P. R. China. E-mail: jason.jsjie@ gmail.com b School of Materials Science and Engineering, Hefei University of Technology, Hefei, Anhui, 230009, P. R. China. E-mail: apjiang@hfut. edu.cn † Electronic supplementary information (ESI) available. See DOI: 10.1039/c1jm11408e This journal is ª The Royal Society of Chemistry 2011 J. Mater. Chem. Dynamic Article Links C < Journal of Materials Chemistry Cite this: DOI: 10.1039/c1jm11408e www.rsc.org/materials PAPER Downloaded by HeFei University of Technology on 20 June 2011 Published on 17 June 2011 on http://pubs.rsc.org | doi:10.1039/C1JM11408E View Online