Development of PC based automation of ion beam analysis and ion implantation experiments

Abstract

This paper presents the details of a personal computer (PC) based automation of ion beam analysis and ion implantation experimental setup that has been developed and implemented in a 1.7 MV Tandetron accelerator. Hardware and software of the PC automated system were designed to automate multiple sample ion implantation, standard Rutherford Backscattering spectrometry (RBS), and High resolution Rutherford Backscattering spectrometry (Hi-RBS) experiments. The system uses in-house developed signal conditioning circuitry, isolation amplifiers, and transistor drivers along with cost-effective and off-the-shelf commercial components like a general purpose, multifunction data acquisition card, etc. A five axis goniometer is used for handling multiple samples and their automatic positioning according to the commands from the PC over RS232 interface. Key tasks carried out in the automation of system include control and mesurement of ion beam fluence, selection of backscattered particles through screening of their energies by controlling a set of +/−25 kV and −3 kV high voltage power supplies, controlled collection of backscattered yield using single and multi channel analysers, controlling the region-of-interest windows in the energy spectra and the cumulative counts in them. Controlling the position of the samples and facilitating the experiments on multiple samples, online display of energy spectra and its auto storage, and vacuum interlocking are also automatically done. This PC based setup has been automated using a windows based LabVIEW software making it easy to port the set up between different computer operating systems apart from achieving many other advantages like quick and easy development of versatile, multi-purpose, and user friendly graphical interface. Extensive tests carried out on the hardware established correct functioning of various modules of the hardware. The 0–10 V control inputs applied to the +/−25 kV and −3 kV high voltage power supplies were tested and seen providing an <0.1% accuracy, <0.05% linearity, very low drift of 50 ppm, 0.01% precision, and <1mv rms output noise. The software modules have been tested to check independent control and monitoring the irradiated dose, energy to voltage conversion, the multi channel analyser control in addition to other tasks such as computing the region-of-interest counts. The fluence computed from the pulse counts from the ion beam current integrator and the actual fluence were found to be matching within 0.1%. The vacuum interlocking scheme was tested covering a range of 10−5 mbar to 10−9 mbar. Hi-RBS was carried out on a 3 nm thick Ag film grown on Si substrate using 0.3 MeV H+ ion beam over a backscattered energy range of 10–300 keV for a fixed ion fluence 2 × 1012 ions/cm2 at each energy. The recorded spectrum showed well separated Si edge and Ag peaks. The energy resolution is calculated to be 1.2 keV and a relative energy resolution (ΔE/E) of ∼0.4% is obtained.