Gaussian distribution of Schottky barrier heights on SnO 2 nanowires
- PDF / 281,876 Bytes
- 6 Pages / 432 x 648 pts Page_size
- 93 Downloads / 248 Views
Gaussian distribution of Schottky barrier heights on SnO2 nanowires Cleber A. Amorim1, Olivia M. Berengue1, Luana Araújo1, Edson R. Leite2 and Adenilson J. Chiquito1 1 Departamento de Física, Universidade Federal de São Carlos, São Carlos, São Paulo – Brazil. 2 Laboratório Interdisciplinar de Eletroquímica e Cerâmicas, Departamento de Química, Universidade Federal de São Carlos, São Carlos, São Paulo – Brazil. ABSTRACT In this work, we studied metal/SnO2 junctions using transport properties. Parameters such as barrier height, ideality factor and series resistance were estimated at different temperatures. Schottky barrier height showed a small deviation of the theoretical value mainly because the barrier was considered fixed as described by ideal thermionic emission-diffusion model. These deviations have been explained by assuming the presence of barrier height inhomogeneities. Such assumption can also explain the high ideality factor as well as the Schottky barrier height and ideality factor dependence on temperature. INTRODUCTION The study of low-dimensional structures has received great attention due to their distinguished performance in electronics, optics and photonics. Because their large surface-tovolume ratio and Debye length comparable to their small size, they demonstrate superior sensitivity to surface chemical processes. Such features make nanostructured materials optimal for use in gas sensor, field effect transistors, bio-chemical sensors, piezoelectric transducers and light-emitting devices, for instance [1-5]. There are several methods to grow nanostructures being the vapor-liquid-solid (VLS) and vapor-solid (VS) widely used because of their simplicity and low costs when compared with MBE or CVD [6]. Several studies have shown the transistor operation with nanometric channels under atmospheric conditions and different oxide thickness [7, 8]. Among the metal oxide materials great emphasis has been given to the SnO2. Because of its wide bandgap (3.8 eV) [9], n-type semiconductor character, high transparency, it has been explored and widely used for transparent conductive electronics whose electrical conductivity depends sensitively on the properties of the surrounding atmosphere. The nanostructured SnO2 has been used as channel in field effect transistors (mostly backgated) used in nanoelectronics as sensors [7,8]. The research on the injection and conduction mechanisms through the SnO2 channel when non-ohmic contacts are observed is poorly reported in literature. The fabrication of electrical contact to nanostructures is very important to field effect transistor (FET) efficiency [10]. In a metal-semiconductor junction the current is controlled by the Schottky barrier which is usually considered homogeneous; the current in such junction are described within the thermionic emission theory [11]:
107
*
2
I = SA T e
−
qφ b 0 kT
qV · § nkT ¨ e − 1¸ ¸ ¨ ¹ ©
(1)
where φb 0 is the metal-semiconductor Schottky barrier height (SBH), S denotes the effective area, A* is the effective Richardson constant,
Data Loading...
