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Electrical transport across pulsed laser deposited zinc oxide (ZnO)/aluminum nitride (AlN)/Si(100) thin film structures has been studied using conducting atomic force microscopy. Current versus voltage spectroscopy performed on the samples with varying AlN layer thickness (t), revealed asymmetric nonlinear behavior with a finite zero current region. The effective barrier height of the system is found to be (∼0.2 eV). The width of the zero current region was found to decrease exponentially with respect to t finally attaining the bulk band gap value. Density functional theory based calculations were carried out on the AlN and AlN-ZnO composite surface to investigate the band gap variation and ZnO adsorption on AlN. Results obtained by these calculations are in harmony with the experimental findings. Calculated values of the bulk cohesive energy explain the growth of the ZnO in an axis perpendicular to the surface supporting the experimentally observed results. Constant voltage current scans studies on the same sample showed the existence of current leakage spots. Current scans performed with varying bias voltages described an unambiguous growth profile of current leakage spots. These leakage spots were observed to evolve in a self similar pattern with the bias, which implied a possible existence of fractal dimension in the pattern of their growth. Mass fractal analysis is therefore carried out to model the growth pattern. Evolution of the mass-fractal with respect to the applied bias is found to be a case of Rayleigh distribution on a two-dimensional Poisson field, in the limiting case. [ABSTRACT FROM AUTHOR]

Pulsed laser deposition technique was used for growing thin films of ZnO on Si (100) substrate held at different temperatures (Ts). All the as-deposited films have shown a preferential c-axis orientation associated with varying grain size as a function of Ts ranging from 100 to 600 °C. Current-voltage (I-V) characteristics of these films show Ohmic behavior over the entire Ts range studied. These films were subjected to annealing at 800 °C in air ambient for 4 h. The grain size was observed to increase after the annealing process for all the films deposited at different Ts. Interestingly, these annealed films show nonlinear variation of current with applied voltage, very similar to the one observed in doped ZnO varistors. The nonlinear parameters such as the asymmetric behavior of change in current on the polarity reversal of voltage, the plateau region, and the break down voltage are observed to depend on Ts. This nonlinear behavior can perhaps be explained on the basis of electronic conduction model proposed for the bulk, doped ZnO varistors. The role of insulating intergranular layers between the disoriented microcrystallites is expected to be similar to that played by insulating intergranular layers in the doped ZnO varistors. [ABSTRACT FROM AUTHOR]

Epitaxial thin films of La[sub 0.67]Ca[sub 0.33]MnO[sub 3] were implanted with 30 and 100 keV [sub 57]Fe ions at different fluence values to achieve a uniform implant distribution. The resistivity of the film increases as fluence increases, but the peak resistivity temperature T[sub p] does not change significantly for the as-implanted sample. Annealing of the implanted samples at 950°C allows recovery of the structural properties of the films and leads to interesting properties: increase of the peak resistivity and of the colossal magnetoresistance values, and decrease of T[sub p]. The decrease in T[sub p] is of ∼130 K, and the increase in resistivity is almost a factor of 28 as compared to the as-implanted sample. [ABSTRACT FROM AUTHOR]

Focuses on a study conducted on thin carbon films deposited on polycrystalline tungsten foil as well as field ion microscope tips by laser-ion deposition in a high-vacuum environment. Structural characterization of the films; Photoelectron spectra of the deposited films; Analysis of Sequence of layers on deposited tungsten.

Focuses on an optical spectroscopy study which examined the role of aluminum in laser ablated YBa[sub2]Cu[sub3]O[sub7-δ] thin films. Advantages of pulsed laser deposition; Analysis of the spectra for aluminum oxide transitions; Generation of aluminum oxide films.

Charge transport across pulsed laser deposited zinc oxide (ZnO)/aluminum nitride (AlN)/Si(100) thin film structures has been studied using conducting atomic force microscopy at different stages of sample preparation. The spatial coverage of current leakage spots could be directly imaged, characterized, and shown to exhibit hysteresis against applied bias voltage. Current-voltage (I-V) measurements on both AlN and ZnO/AlN/Si(100) structure exhibited asymmetric nonlinear behavior with a large zero current region. Further analysis of I-V and current-force data suggests Fowler–Nordheim like behavior under Hertzian contact as a dominant mechanism for electron transport. [ABSTRACT FROM AUTHOR]

Pulsed laser induced reactive quenching at a liquid–solid interface was used for the synthesis of tetrahedrally coordinated crystalline carbon nitride on a tungsten substrate. The crystalline phase was identified by transmission electron diffraction. X-ray photoelectron spectroscopy indicated that the carbon atoms are coordinated only tetrahedrally with nitrogen—as expected for C3N4. The atomic percentage of N (considering only those atoms coordinated with C) is about 35%. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Epitaxial films of La[sub 2/3]Ca[sub 1/3]MnO[sub 3] were successively implanted with 100 and 200 keV silver ions at fluences of 4.5x10[sup 15] and 1x10[sup 16] ions/cm[sup 2], respectively, to achieve a fairly uniform implant distribution. The as-implanted films are insulating and do not show a metal-insulator transition. Postimplantation annealing at 950 °C shows a recovery of the high structural quality of the films, along with an increase in the metal-insulator transition temperature (T[sub p]), magnetoresistance, and the peak temperature coefficient of resistance (TCR) at the transition. The peak TCR of 23% for manganite films is clearly significant for bolometric applications. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]