Structural properties of SnO₂ nanowires and the effect of donor like defects on its charge distribution

Abstract

Tin oxide (SnO 2 ) nanowires (NWs) with diameters of 50 nm, lengths up to 100 mm and a tetragonal rutile crystal structure have been grown by low pressure reactive vapour transport on 1 nm Au/Si(001). The free carrier density of the SnO 2 NWs measured by THz absorption spectroscopy was found to be n ¼ (3.3 AE 0.4) Â 10 16 cm À3 . Based on this we have determined the one-dimensional (1D) sub-band energies, overall charge distribution and band bending via the self-consistent solution of the Poisson-Schrödinger equations in cylindrical coordinates and in the effective mass approximation. We find that a high density of 10 18 -10 19 cm À3 donor-like defect related states is required to obtain a line density of 0.7 Â 10 9 close to the measured value by taking the Fermi level to be situated %0.7 eV below the conduction band edge at the surface which gives a surface depletion shell thickness of 15 nm. We discuss the origin of the donor-like states that are energetically located in the upper half of the energy band gap as determined by ultrafast, time-resolved absorption-transmission spectroscopy.

Broad compositional tunability of indium tin oxide nanowires grown by the vapor-liquid-solid mechanism

“…This is in agreement with selected area electron diffraction (SAED) pattern and HRTEM analysis carried out previously on SnO 2 NWs obtained using the same growth conditions, which verified that they crystallize in the tetragonal rutile phase belonging to the P42 /mnm space group with lattice constants of a = 0.4738 nm and c = 0.3186 nm. 15 Similarly, the reaction of In and Sn with O 2 over the 1 nm Au/Si(001) using exactly the same growth conditions lead to the growth of ITO NWs with diameters of a few tens of nm's and lengths up to 100 μm as shown in Fig. 1(a) but they appeared as a light green layer.…”

Promotion of acceptor formation in SnO2 nanowires by e-beam bombardment and impacts to sensor application

“…In this study, we assume μ e  = 5 ×  μ h . The factor 5 is assigned on the basis of the effective mass ratio of a hole and an electron4041. Therefore, we consider μ h  = 72/5 = 14.4 cm 2 /(V·s).…”

Acceptor-Compensated Charge Transport and Surface Chemical Reactions in Au-Implanted SnO2 Nanowires

“…Our measured resistivity of pristine SnO 2 ( n -type) can be reproduced reasonably from the semiconductor theory; specific resistivity = 1/( qμ e n ), in which q , μ e , and n are the elementary charge, mobility, and concentration of electrons, respectively. By taking the values of q = 1.6 × 10 −19 C, μ e = 72 cm 2 /(V·s) 14 , and n = 3.3 × 10 16 cm −3 15 , we obtain a specific resistivity of 2.63 ohm/cm. Using our measured resistivity, the equivalent length of nanowires is calculated to be 38023 cm, which will be applied to convert the measured resistance data to the specific resistivity, as shown below.…”