T. Szörényi

Excimer laser processing of indium‐tin‐oxide films: An optical investigation

dc sputtered indium‐tin‐oxide films have been excimer laser irradiated at subablation threshold fluences (<510 mJ/cm2). Optical characterization of irradiated products has been performed aiming at resolving the finer structure appearing in the IR–visible absorption spectra, as a function of laser fluence, and assigning such features to specific electronic defects which are produced upon irradiation. Four individual Gaussian‐like contributions to absorption spectra are identified at 0.7, 1.0, 1.6, and 2.6 eV, the intensity of which is observed to vary with fluence. Being absent in the original films and emerging in optical spectra at fluences exceeding 300 mJ/cm2, the 2.6 eV contribution is most characteristic to excimer laser processing and is responsible for the darkening of the film. Thermal model calculations reveal that such defects are produced only upon melting and fast resolidification of the film. The evolution of the chemistry actually taking place in the film upon irradiation is followed by x‐ra...

Ar+ laser-induced forward transfer (LIFT): a novel method for micrometer-size surface patterning

Abstract As a result of a systematic study on laser-induced forward transfer of tungsten (W) thin films by a focused Ar+ laser (λ=514 nm, 2w0=3μm), it is shown that deposition of 2–3μm diameter W spots of 100 nm thickness and 100% coverage is attainable at low processing powers (50–100 mW).

Deposition of micrometer-sized tungsten patterns by laser transfer technique

A simple single‐step technique for surface patterning is presented. It is shown that well‐adhering micrometer‐sized patterns of 100% coverage preserving the shape and dimensions of the ablated area can be deposited by ablating and transferring tungsten thin films in the form of single solid pieces using single pulses of peak power up to 100 mW and 100 μs–1 ms duration from a diode‐pumped YAG laser.

Laser induced forward transfer: The effect of support-film interface and film-to-substrate distance on transfer

A comparative study on metal pattern deposition of mm2-area by ablating chromium and titanium thin films from an optically transparent support and transferring the ablated material onto another substrate in close proximity with a single laser pulse (LIFT) is reported. The role of support-film interface and film-to-substrate distance in determining both ablation and transfer is discussed. The sequence of events as a function of processing fluence is interpreted by comparing experimental data with calculated temperature distributions. In the case of poorly adhering films the transfer yield is independent of film-to-substrate distance between 0 and 60 μm throughout the fluence range studied. The transmittance of the ablated areas of well adhering films decreases and that of the corresponding prints increases with increasing distance as evaporation becomes dominant.

Pulsed laser ablative deposition of thin metal films

Abstract Different mechanisms of pulsed laser ablation and ablative deposition of thin metal films at various fluences are discussed. The window for clear ablation, i.e. the fluence range in which the film is completely removed without any damage of the supporting substrate and the window for best quality printing are determined.

Metal pattern deposition by laser-induced forward transfer

Abstract Results of a systematic study on laser-induced transfer of metal patterns are summarized. The pulse width of the lasers used in the experiments was scaled from a few nanoseconds to one millisecond to discover the different time-dependent processes determining ablation and transfer of thin films of a variety of metals. The physical events were followed by optical and electron microscopy and static and time-resolved optical measurements, as well as ultrafast photography. The main conclusion is that the adhesive properties of the interface between the metal film and the support, and the thermophysical characteristics of both the support and target substrates determine the yield of the transfer. Optimum parameter sets ensuring deposition of well adhering micrometer-sized patterns faithfully reproducing the illuminating area were determined. The technological importance of this novel technique is pointed out.

Atypical characteristics of KrF excimer laser ablation of indium-tin oxide films

Abstract Indium-tin oxide films possess ablation characteristics which are a function of the film thickness. For 70 and 160 nm thicknesses, low-fluence single pulses are sufficient to remove from the support the solid phase oxide film over the whole illuminated area. Processing under such conditions offers a rather convenient means for large-area “clean” surface patterning, which is, however, limited at high fluences by the onset of melting. At fluences higher than this onset, layer-by-layer ablation via evaporation sets in. For thicker films, only ablation via evaporation is possible. These experimental findings are interpreted in the framework of a thermal model which is supported by appropriate numerical calculations of the temperature distribution in these films.

Kr+ laser-induced chemical vapor deposition of W

Kr+ laser‐induced pyrolytic direct writing of W stripes by H2 reduction of WF6 has been investigated. The reproducibility of the process and the morphology and electrical properties of deposits depend heavily on the partial pressures of both WF6 and H2; the best results have been obtained with p(WF6)=5 mbar and 100 mbar≤p(H2)≤800 mbar. For a laser focus of 2w0=7 μm and laser powers between 30 and 200 mW, the widths of stripes varied between 1.5 and 15 μm with corresponding thicknesses between 0.1 to 3 μm. The width of stripes is independent of the scanning speed within the range 20 μm/s≤Vs ≤400 μm/s. The electrical resistivities of these stripes were about a factor of 1.3–2.3 larger than the bulk value.

Structural characterization of amorphous vanadium pentoxide thin films prepared by chemical vapour deposition /CVD/

Abstract Amorphous vanadium pentoxide thin films were prepared by CVD of VOCl 3 with H 2 O at room temperature. The amorphous- to-crystalline transition temperature of the material was found at about 240°C. The DTA curves and IR spectra showed that the films contained water. The V 4+ content of the films was estimated from quantitative EPR measurements. The results verify that CVD is an appropriate method to produce near stoichiometric / V 4+ content: 1.5–2.0% / amorphous vanadium pentoxide thin films.

Dynamics of long-pulse laser transfer of micrometer-sized metal patterns as followed by time-resolved measurements of reflectivity and transmittance

Laser‐induced transfer of thin films is a simple single‐step technique for surface patterning. In this paper the optimization principles and processes are outlined which led to successful application of the long‐pulse laser transfer technique. The critical analysis of experiments on ns‐pulse laser transfer of thin films of a variety of metals and the optimization study of the long‐pulse laser transfer technique suggests that efficient deposition of high‐quality patterns of micrometer dimensions can only be expected when using long laser pulses which not only produce ablation of the thin film pattern in solid phase but also maintain sufficient temperature during transfer and even on landing, to ensure film adherence. In order to identify and understand the different time‐dependent processes determining the laser transfer, studies using optical and electron microscopy and static and time‐resolved optical measurements were performed.