Thick Indium Tin Oxide Research Articles

Electrical and optical properties of indium tin oxide thin films grown by pulsed laser deposition

Indium tin oxide (ITO) thin films (200–400 nm in thickness) have been grown by pulsed laser deposition (PLD) on glass substrates without a post-deposition anneal. The electrical and optical properties of these films have been investigated as a function of substrate temperature and oxygen partial pressure during deposition. Films were deposited at substrate temperatures ranging from room temperature to 300 °C in O2 partial pressures ranging from 0.1 to 100 mTorr. For 300 nm thick ITO films grown at room temperature in oxygen pressure of 10 mTorr, the electrical conductivity was 2.6×10-3 Ω-1cm-1 and the average optical transmittance was 83% in the visible range (400–700 nm). For 300 nm thick ITO films deposited at 300 °C in 10 mTorr of oxygen, the conductivity was 5.2×10-3 Ω-1cm-1 and the average transmittance in the visible range was 87%. Atomic force microscopy (AFM) measurements showed that the RMS surface roughness for the ITO films grown at room temperature was ∼7 A, which is the lowest reported value for the ITO films grown by any film growth technique at room temperature.

Visible electroluminescence from Eu:CaF2 layers grown by molecular beam epitaxy on p-Si (100)

Visible electroluminescence (EL) is observed at room temperature by current injection into Eu:CaF2 layers containing 7.5 and 8.0 at. % Eu grown by molecular beam epitaxy on lightly doped (100) p-type silicon. The EL spectra are broad with peaks near 700 and 600 nm, respectively. Room temperature photoluminescence spectra for the same samples exhibited peaks near 420 nm, with higher doped samples showing a more pronounced long wavelength tail. Although both metal and indium–tin–oxide (ITO) contacts were successfully used for current injection, the best EL intensity stability was achieved with contacts made of a 100 Å thick Al layer covered by a 2500 Å thick ITO layer.

Strongly modified emission from organic electroluminescent device with a microcavity

We demonstrate the improvements of directionality and intensity of light emission from the electroluminescent (EL) device with a Fabry-Perot microcavity. The improvements have been realized by applying a new idea: (1) an unsymmetrical emission spectrum, with a steep rise at shorter wavelength side, from the emitting region doped with quinacridone, and (2) a composite dielectric mirror including a thick indiumtin-oxide (ITO) conducting layer. The resultant microcavity EL device exhibited a single mode emission with pure green (full width at half-maximun, FWHM = 15 nm at 535 nm), and the emission intensity for normal direction (along the optical axis of the device) was significantly enhanced. The sharply directed emission exceeded 40 000 cd/m 2 at a driving current of 800 mA/cm 2, which was higher than that of a noncavity EL device.

Microwave plasma assisted sputtering

Indium tin oxide (ITO) films were prepared on SiO 2 and on resin coated glass by microwave assisted sputtering and by magnetron dc sputtering using ITO targets. To find out the advantages of the microwave assisted sputtering in comparison to the magnetron sputtering the results of the two methods are compared. At substrate temperatures of 200°C ITO films with a specific resistivity of 133 μΩ cm at a film thickness of 100 nm could be prepared by microwave assisted sputtering, whereas the smallest obtained specific resistivity of the ITO films by the magnetron process was 212 μΩ cm. From Hall measurement it can be seen, that the reduced specific resistivity is mainly caused by the increased carrier density. On resin coated glass substrates the specific resistivity of 100 nm thick ITO films could be reduced by the microwave assisted sputtering process from 226 μΩ cm for the magnetron process to 175 μΩ cm. Also from Hall measurement this reduction in the specific resistivity is affected by an increase of the carrier mobility. Secondary ion mass spectroscopy analyses show, that the higher specific resistivity in the ITO films on resin coated glass in comparison to the films on SiO 2 coated glass is at least partly affected by the larger carbon content in the films. This carbon results from the outgassing of the resin. By the microwave assisted sputtering method the optical properties of ITO films could be improved about 1.5% on resin coated glass substrates. For the SiO 2 coated substrates the maximum transmittance for the two methods was nearly the same.

RF sputtered indium-tin-oxide as antireflective coating for GaAs solar cells

Conductive and antireflective indium-tin-oxide (ITO) has been prepared by RF sputtering in Ar atmosphere, without introducing oxygen into the plasma and on room temperature substrates in order to be used as antireflective coating on GaAs solar cells. The electrical resistivity of the n-type, degenerate ITO films exhibited a reduction with deposition rate and an increase with total pressure, while it was independent of the film thickness in the range of 20 nm to 130 run. Further reduction of resistivity, up to 4 × 10 −4 Ωcm, was obtained by annealing at 400°C. This is the lowest resistivity that has been reported for TTO films prepared under similar conditions. The transmittance of 90 nm thick ITO film was 85% and the reflectance of p/n GaAs solar cell was reduced from 35% to 2% after the ITO layer application.

Comprehensive evaluation of ITO thick films produced under optimum annealing conditions

Abstract Indium-tin-oxide (ITO) is a transparent semiconductor that can be formed so that it exhibits a very low resistivity. The applications of this material include solar cells, photodetectors, and transparent contacts for devices such as flat panel displays, and touch sensitive cathode ray tube screens. The authors have investigated the role of both vacuum and reducing atmosphere (N 2 + H 2 ) annealing on the properties of thick film ITO. Both vacuum annealing and forming gas (N 2 + H 2 ) annealing result in films with significantly lower resistivity than unannealed films. Samples with sheet resistances of 150 Ω/square have been produced. These values are the lowest reported to date for ITO thick films. Optical characterization including transmission and reflectivity have been conducted, as well as examination of the conductivity as a function of temperature.

A photoetched cell relocation matrix for long-term, quantitative observations of selected individual neurons in culture

A photoetched matrix of indium tin oxide (ITO) on glass has been developed and tested as a tool to assist in the relocation and identification of individual neuronal cells in culture. The matrix is formed by 10–15 μm wide and 300 Å thick ITO lines which subdivide a 1-cm 2 area into 625 smaller squares. Each of the smaller squares measures 400 μm on a side and contains a photoetched two-letter “address”. The address code allows precise relocation of specific regions of a culture as well as verification of the identities of individual neurons selected for repeated observation. Marks at 50 μm intervals along the sides of the address squares permit quantitative analysis of morphological changes, cell migration, reaggregation, etc. The ITO is transparent and does not interfere with visualization of even fine details of cells with high power microscopy.