Photoconductivity in anodic Ta2O5 formed on nitrogen-doped tantalum films

Abstract

Photocurrent spectroscopy (or the spectral response of photoconductivity) and transient photoconductivity have been used to probe the defect structure (trap states) of anodic Ta2O5 films formed on pure and nitrogen-doped sputter-deposited tantalum. Results of this investigation indicate the presence of two trap-related responses at 1.5 and 2.8 eV, respectively. Nitrogen in the oxide is found to compensate these traps, that is, the amplitude of the photocurrent response is observed to decrease with increasing nitrogen concentration. The recombinationlike trap at 2.1 eV, present in pure Ta2O5, is not observed in samples doped with as little as 2 at.% N2. Transient results indicate a spatial localization of the 1.5-eV trap which may be related to the nonuniform nitrogen distribution in the oxide. Nitrogen in the oxide was found to have little effect on the band-gap energy (4.4 eV).

High room-temperature photoluminescence of one-dimensional Ta2O5nanorod arrays

“…PL) and energy is released during the radiative transitions. Also, dangling bonds can provide numerous trap-level states, but only the trap level of 2.19 eV is the intrinsic midgap state [41][42][43][44][45][46][47][48][49]. Hence, the energy bandgap of the 1D Ta 2 O 5 nanorod array is ∼4.4 eV, which agrees with the results in previous reports [43,51,52].…”

“…In earlier experimental studies [41][42][43][44][45][46][47][48][49] some trap levels and shallow centers of oxygen vacancies in the bandgap of Ta 2 O 5 have been observed.…”

“…The broadening of the a, c, d and e peaks is caused by variations in the number of types of oxygen vacancies. However, the sharp b peak represents the large number of oxygen vacancies of the intrinsic midgap state [41][42][43][44][45][46][47][48][49].…”

“…Also, dangling bonds can provide numerous trap-level states, but only the trap level of 2.19 eV is the intrinsic midgap state [41][42][43][44][45][46][47][48][49]. Hence, the energy bandgap of the 1D Ta 2 O 5 nanorod array is ∼4.4 eV, which agrees with the results in previous reports [43,51,52]. The 1D Ta 2 O 5 nanorod array has a wide bandgap of ∼4.4 eV, making it more suitable for ultraviolet (UV) and blue optoelectronic applications.…”

Correlation between Electrical and Optical Properties of Tantalum Anodic Oxide and Electron Cyclotron Resonance Etching Studies of E-Beam Deposited Ta2O5Films

“…11 Two papers 12,13 have reported trap energies of 1.5 eV and 2.1 eV for anodic Ta 2 O 5 films grown on sputtered Ta. It was found 12,13 that the 2.1 eV trap was a positive Coulombic center. This 2.1 eV energy corresponds to 593 nm.…”