Laser plasma ion implantation and deposition of platinum for SiC-based hydrogen detector fabrication

Abstract

A pulsed plasma plume obtained by pulsed laser irradiation of a Pt target was used to fabricate a hydrogen sensor on a 6H–SiC single crystal by means of ion implantation followed by thin film deposition. To realize the ion implantation, high voltage pulses with positive polarity were applied to the Pt target when the laser plasma expanded from the target to the SiC substrate. Experimental diagnostics of pulsed ion beams extracted from laser-produced plasma were performed and the structure of the SiC crystal after high-temperature (500°C) ion implantation was studied by Rutherford backscattering spectroscopy of 4He+ ions. At the same time, a one-dimensional model of the plasma movement in a pulsed electric field was developed and simulations were carried out using the particle-in-cell method. Modeling allowed determination of the ion energy distribution depending on the delay time of the high voltage pulse after the laser pulse. The calculated energy distribution of Pt ions was used to predict the depth profile of implanted Pt ions in the SiC substrate. The predicted profile agreed sufficiently well with the experimentally measured depth distribution of Pt in the SiC substrate. To characterize the fabricated SiC sensor, the current flow through a barrier structure was studied. The volt–ampere characteristics of the structure were measured in air and in a mixture of air and hydrogen (2%) at a temperature of 500°C. The characteristic value of the change in voltage exceeded 2V at the bias current of 1mA when hydrogen was added to the air. The response of the sensor to the hydrogen was stable after long-term tests while the structure of the Pt film was disturbed. The ion-implanted layer operated as a series resistance, which had a significant effect on the current flow through the barrier structure. The resistance decreased under the influence of hydrogen and persisted during long-term tests.