Wide Range Photodetector Based on Catalyst Free Grown Indium Selenide Microwires Zulfiqar Ali, † Misbah Mirza, ‡ Chuanbao Cao,* ,† Faheem K. Butt, † M. Tanveer, † Muhammad Tahir, † Imran Aslam, † Faryal Idrees, † and Muhammad Safdar ‡ † Research Centre of Materials Science, School of Materials Science and Engineering, Beijing Institute of Technology, Beijing100081, People’s Republic of China ‡ National Center for Nanoscience and Technology, Chinese Academy of Sciences, Beijing 100190, People’s Republic of China ABSTRACT: We first report the catalyst free growth of indium selenide microwires through a facile approach in a horizontal tube furnace using indium and selenium elemental powders as precursors. The synthesized microwires are γ-phase, high quality, single crystalline and grown along the [112̅0] direction. The wires have a uniform diameter of ∼1 μm and lengths of several micrometers. Photodetectors fabricated from synthesized microwires show reliable and stable photoresponse exhibiting a photoresponsivity of 0.54 A/W, external quantum efficiency of 1.23 at 633 nm with 4 V bias. The photodetector has a reasonable response time of 0.11 s and specific detectivity of 3.94 × 10 10 Jones at 633 nm with a light detection range from 350 to 1050 nm, covering the UV-vis-NIR region. The photoresponse shown by single wire is attributed to direct band gap (E g = 1.3 eV) and superior single crystalline quality. The photoresponsive studies of single microwires clearly suggest the use of this new and facile growth technique without using catalysts for fabrication of indium selenide microwires in next-generation sensors and detectors for commercial and military applications. KEYWORDS: indium selenide, catalyst free growth, microwires, photodetector, semiconductor ■ INTRODUCTION One-dimensional (1D) crystal structures are important for optoelectronics and future nanoscale devices as they allow interconnections within their size limits. 1-9 There are reports on nanoscale device fabrication and these devices have shown significant progress in building a new generation of electronic and photoelectronic systems. 10-14 Photodetectors are necessary devices in memory storage and optoelectronic circuits and various semiconducting materials like group III-V compounds and group II-VI compounds 15-17 have been used in fabricating photodetectors but are limited due to poor efficiency. Indium selenide (In 2 Se 3 ) is an important narrow band gap III-V semiconducting material with a layered crystal structure. It usually crystallizes into double layers consisting of the [Se-In- Se-In-Se] stacked together through Se atoms along the c- axis. 18 Highly anisotropic structural, electrical, optical and mechanical characteristics of this material 19 make the phase attractive for photovoltaic solar cells, ionic batteries, optoelec- tronic and phase change memory devices. 20-25 However, most of the work is reported on indium selenide thin films; 26-29 only a limited number of reports focus on 1D growth of indium selenide nanostructures and its potential properties for applications in electronic, optoelectronic, phase change memory and thermoelectric devices. All such reports accentuate on the catalyst assisted growth of wires or rods through a VLS growth mechanism, 30-34 thus obtaining the α-phase of this material. There is only one report on catalyst free growth of indium selenide 35 using In 2 Se 3 as a precursor but the phase reported is InSe in 1:1 stoichiometric ratios. The reason for no such reports has been the difficulty in controlling the chemical reaction and morphology at the same time. On the other hand, using a catalyst (usually Au) for 1D nanostructures not only makes the growth expensive but also Au particles are incorporated in the crystal during the growth, thus adding impurity in the crystal structure. The photo- response exhibited by such structures cannot be considered purely due to indium selenide. We report here for the first time, the growth of pure phase γ- In 2 Se 3 without utilizing any catalyst; we not only control the chemical reaction but also obtain high yield, ultralong and high quality indium selenide (In 2 Se 3 ) microwires using elemental indium and selenium powders as precursors through a vapor- solid (VS) approach. Furthermore, single microwire In 2 Se 3 photodetectors are fabricated and photoresponse characteristics were schematically examined under a broad light range from 350 to 1050 nm. The photodetector shows appreciable performance in this broad wavelength range. The results suggest that catalyst free growth of In 2 Se 3 in a 1D structure with controlling diameters will open a gateway toward the Received: March 30, 2014 Accepted: May 17, 2014 Published: May 17, 2014 Research Article www.acsami.org © 2014 American Chemical Society 9550 dx.doi.org/10.1021/am501933p | ACS Appl. Mater. Interfaces 2014, 6, 9550-9556