Electrical characteristics of nickel silicide–silicon heterojunction in suspended silicon nanowires Su Heon Hong a,b , Myung Gil Kang a,b , Byung-Sung Kim a,c , Duk Soo Kim a,b , Jae Hyun Ahn a,b , Dongmok Whang a,c,⇑ , Sang Hoon Sull b , Sung Woo Hwang a,b,⇑ a Research Center for Time-domain Nano-functional Devices, Korea University, 5-1 Anam, Sungbuk, Seoul 136-701, Republic of Korea b School of Electrical Engineering, Korea University, 5-1 Anam, Sungbuk, Seoul 136-701, Republic of Korea c School of Advanced Materials Science and Engineering, Sungkyunkwan University, 300 Cheoncheon, Jangan, Suwon, Gyeonggi 440-746, Republic of Korea article info Article history: Received 27 May 2010 Received in revised form 4 November 2010 Accepted 9 November 2010 Available online xxxx The review of this paper was arranged by Prof. A. Zaslavsky Keywords: Silicon nanowire Electron transport Silicide–silicon heterojunction abstract Electronic characteristics of silicide/silicon interface were studied in the suspended, chemically synthe- sized silicon nanowires (SiNWs). Step-by-step intrusion of a silicide/Si interface along the axial direction of a suspended silicon nanowire was performed by repeated thermal annealing cycles, and the current– voltage (I–V) characteristics of the annealed silicide/SiNW/silicide structure were measured at each cycle. The intruded length of the silicide was found to be directly proportional to the total annealing time, but the rate of silicidation was much smaller than previous works on similar silicide/SiNWs. A structural kink with Ni atoms diffused along the sidewall created a secondary source of silicidation, resulting in anom- alous I–V characteristics. The measured I–V including this unintentional silicidation in the Si channel was explained by various combinations of Schottky barriers and resistors. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Chemically synthesized silicon nanowires (SiNWs) have at- tracted much attention because of their wide range of potential applications in high performance field effect transistors [1–7], bio- sensors [8], flexible devices [9], and even field emission sources [10]. One main route of connecting these devices to other devices and circuits is through metal–SiNW contacts. These contacts have small cross-sections, and it is difficult to understand their metal- lurgical properties and electronic transport mechanisms. Silicide–Si hetero-structures are widely used for the source– drain contacts of conventional silicon devices, and they have natu- rally been introduced in the chemically synthesized SiNWs. The most common way to form silicide/silicon nano-heterojunctions is to thermally drive silicidation of either Ni [11–14] or Pt [15]. Most of these studies successfully showed the enhanced transcon- ductance originated from reduced contact resistance and increased gate efficiency. Furthermore, additional physical phenomena including ballistic transport and high speed switching were possi- ble due to the abrupt change of the chemical composition at the silicide/Si interface [16]. The position of the silicide/Si interface is important in the device characteristics because it determines the channel length of the transistor. However, a systematic study on the movement of the silicide/Si interface with respect to the annealing condition and its electronic properties have seldom been reported. The only exception is the recent work on a Cu 3 Ge/Ge NW system exhibiting movement of the atomically sharp interface [17] by a few steps of annealing. In this paper, we performed repeated thermal annealing on dielectrophoretically aligned, suspended SiNWs with NiCr con- tacts. Our suspended structure prevents a possible interaction be- tween the SiNW and the substrate during the annealing process. We examined the position of the silicide/Si interface as a function of total annealing time. The current–voltage (I–V) characteristics were measured after each annealing cycle and the linear resistance as a function of total annealing time was analyzed. In addition to the intrusion from the contacts, unintentional silicidation from a structural kink in the middle of the SiNW was considered to ex- plain the measured I–V characteristics. 2. Experiments The n-type SiNWs used in this experiment were synthesized by a catalyst-free vapor–solid (VS) process [18], and their diameters 0038-1101/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.sse.2010.11.012 ⇑ Corresponding authors. Address: Research Center for Time-domain Nano- functional Devices, Korea University, 5-1 Anam, Sungbuk, Seoul 136-701, Republic of Korea. Tel.: +822 32903241; fax: +822 9210544 (S.W. Hwang), School of Advanced Materials Science and Engineering, Sungkyunkwan University, 300 Cheoncheon, Jangan, Suwon, Gyeonggi 440-746, Republic of Korea. Tel.: +822 32903241; fax: +822 9210544 (D. Whang). E-mail addresses: dwhang@skku.edu (D. Whang), swhwang@korea.ac.kr (S.W. Hwang). Solid-State Electronics xxx (2010) xxx–xxx Contents lists available at ScienceDirect Solid-State Electronics journal homepage: www.elsevier.com/locate/sse Please cite this article in press as: Hong SH et al. Electrical characteristics of nickel silicide–silicon heterojunction in suspended silicon nanowires. Solid State Electron (2010), doi:10.1016/j.sse.2010.11.012