Effect of annealing on properties of sputtered and nitrogen-implanted ZnO:Ga thin films

Thin films of gallium-doped zinc oxide (ZnO:Ga) were deposited on Corning glass substrates by rf diode sputtering and then implanted with 180 keV nitrogen ions in the dose range of 1 × 1015 ÷ 2 × 1016 cm-2. After the ion implantation, the films were annealed under oxygen and nitrogen ambient, at different temperatures and time, and the effect on their microstructure, type and range of conductivity, and optical properties was investigated. Post-implantation annealing at 550 °C resulted in n-type conductivity films with the highest electron concentration of 1.4 × 1020 cm-3. It was found that the annealing parameters had a profound impact on the film’s properties. A p-type conductivity (a hole concentration of 2.8 × 1019 cm-3, mobility of 0.6 cm2/V s) was observed in a sample implanted with 1 × 1016 cm-2 after a rapid thermal annealing (RTA) in N2 at 400 °C. Optical transmittance of all films was >84% in the wavelength range of 390–1100 nm. The SIMS depth profile of the complex 30NO− ions reproduces well a Gaussian profile of ion implantation. XRD patterns reveal a polycrystalline structure of N-implanted ZnO:Ga films with a c-axis preferred orientation of the crystallites. Depending on the annealing conditions, the estimated crystallite size increased 25 ÷ 42 nm and average micro-strains decreased 1.19 × 10-2 ÷ 6.5 × 10-3 respectively

Effect of annealing on properties of sputtered and nitrogen-implanted ZnO:Ga thin films

Thin films of gallium-doped zinc oxide (ZnO:Ga) were deposited on Corning glass substrates by rf diode sputtering and then implanted with 180 keV nitrogen ions in the dose range of 1 × 1015 ÷ 2 × 1016 cm-2. After the ion implantation, the films were annealed under oxygen and nitrogen ambient, at different temperatures and time, and the effect on their microstructure, type and range of conductivity, and optical properties was investigated. Post-implantation annealing at 550 °C resulted in n-type conductivity films with the highest electron concentration of 1.4 × 1020 cm-3. It was found that the annealing parameters had a profound impact on the film’s properties. A p-type conductivity (a hole concentration of 2.8 × 1019 cm-3, mobility of 0.6 cm2/V s) was observed in a sample implanted with 1 × 1016 cm-2 after a rapid thermal annealing (RTA) in N2 at 400 °C. Optical transmittance of all films was >84% in the wavelength range of 390–1100 nm. The SIMS depth profile of the complex 30NO− ions reproduces well a Gaussian profile of ion implantation. XRD patterns reveal a polycrystalline structure of N-implanted ZnO:Ga films with a c-axis preferred orientation of the crystallites. Depending on the annealing conditions, the estimated crystallite size increased 25 ÷ 42 nm and average micro-strains decreased 1.19 × 10-2 ÷ 6.5 × 10-3 respectively

Carrier Control in Polycrystalline ZnO:Ga Thin Films via Nitrogen Implantation Electronic Materials and Processing

The electrical characteristics of gallium-doped zinc oxide (ZnO:Ga) thin films prepared by rf diode sputtering were altered via nitrogen implantation by performing two implants at 40 keV and 80 keV with doses of 1×1015 and 1×1016 cm−2 to achieve a p-type semiconductor. An implantation of 1×1015 cm−2 N+-ions yielded a p-type with hole concentrations 1017–1018 cm−3 in some as-implanted samples. The films annealed at temperatures above 200°C in O2 and above 400°C in N2 were n-type with electron concentrations 1017–1020 cm−3. The higher nitrogen concentration (confirmed by SRIM and SIMS), in the films implanted with a 1×1016 cm−2 dose, resulted in lower electron concentrations, respectively, higher resistivity, due to compensation of donors by nitrogen acceptors. The electron concentrations ratio n(1×1015)/n(1×1016) decreases with increasing annealing temperature. Hall measurements showed that 1×1016 cm−2 N-implanted films became p-type after low temperature annealing in O2 at 200°C and in N2 at 400°C with hole concentrations of 3.2×1017 cm−3 and 1.6×1019 cm−3, respectively. Nitrogen-implanted ZnO:Ga films showed a c-axes preferred orientation of the crystallites. Annealing is shown to increase the average transmittance (>80%) of the films and to cause bandgap widening (3.19–3.3 eV)

Carrier Control in Polycrystalline ZnO:Ga Thin Films via Nitrogen Implantation

The electrical characteristics of gallium-doped zinc oxide (ZnO:Ga) thin films prepared by rf diode sputtering were altered via nitrogen implantation by performing two implants at 40 keV and 80 keV with doses of 1 x 10(15) and 1 x 10(16) cm(-2) to achieve a p-type semiconductor. An implantation of 1 x 10(15) cm(-2) N+-ions yielded a p-type with hole concentrations 10(17)-10(18) cm(-3) in some as-implanted samples. The films annealed at temperatures above 200 degrees C in O-2 and above 400 degrees C in N-2 were n-type with electron concentrations 10(17)-10(20) cm(-3). The higher nitrogen concentration (confirmed by SRIM and SIMS), in the films implanted with a 1 x 10(16) cm(-2) dose, resulted in lower electron concentrations, respectively, higher resistivity, due to compensation of donors by nitrogen acceptors. The electron concentrations ratio n((1) (x) (1015))/ n((1 x 1016)) decreases with increasing annealing temperature. Hall measurements showed that 1 x 10(16) cm(-2) N-implanted films became p-type after low temperature annealing in O-2 at 200 degrees C and in N-2 at 400 degrees C with hole concentrations of 3.2 x 10(17) cm(-3) and 1.6 x 10(19) cm(-3), respectively. Nitrogen-implanted ZnO:Ga films showed a c-axes preferred orientation of the crystallites. Annealing is shown to increase the average transmittance ( GT 80%) of the films and to cause bandgap widening (3.19-3.3 eV). (C) 2012 The Electrochemical Society. All rights reserved