A review of bubble energetics is presented to provide background into gas saturation and bubble formation in
semiconductor resists. Nitrogen was used as a drive gas to push liquid out of several package materials versus a
mechanical pump. The incorporation of dissolved gas was measured and a barrier liner was found to be superior
versus a bottle with no liner. We have demonstrated that a pressure dispense package with an appropriate barrier
liner provides a means to deliver lithographic chemicals and resist without the use of a mechanical pump.
The transport properties of electrons and holes in mercuric iodide determine the performance of detectors. The relatively low levels of these properties limit the volume of detectors with high spectral resolution that can be fabricated and leads to long pulse collection times. These transport parameters can be increased by optimizing the material processing, the crystal growth, and the detector fabrication. This paper will present our own results obtained by analysis of individual pulse shapes. The values for the mobilities generally measured are between 60-90 cm2/Vsec for electrons and 2-4 cm2/Vsec for holes. These results will be compared with the values published by other investigators. Possible reasons for the differences in the reported values will be discussed and explanations will be suggested.
The performance of semiconductor radiation detectors is a function of electronic properties which are in turn related to crystallographic quality. In this paper we used devices from <100> and <110> growth regions of several different HgI2 crystals grown by the PVD method. We measured I/V characteristics of HgI2 devices over the range of +/-1000V. Voltages were ramped at different rates and at a range of temperatures (-70oC to +20oC) and the dark current decreased with temperature. Several devices exhibited negative differential resistance indicating field enhanced trapping and/or the formation of high-field domains. These devices exhibited NDR at both positive and negative voltages and it was observed that the current peak reduced with repeated cycling of positive bias indicating the reduction of carriers with time. After applying a negative bias, the current peak on the positive bias increased dramatically indicating that the traps were repopulated. These experimental results were modeled with several analytical expressions of conduction processes, considering both semiconductor and insulator models, e.g., Frenkel-Poole, Schottky, and space-charge-limited emission, toward lending insight to mechanisms resulting in HgI2 detector conditioning.
We investigated bulk-grown HgI2 crystals to better understand the nature of crystallographic defects and strain/stress in different growth regions of the crystal and their affect on the performance of HgI2-based radiation detectors. Double-axis and triple-axis high-resolution x-ray diffraction were used to characterize the mosaic structure and strain in HgI2. Rocking curves revealed significant mosaic spreading in <110> growth regions exhibiting X-defects versus X-defect-free <100> growth regions. Both <110> and <100> growth regions exhibited little strain (~0.01%). We report the narrowest rocking curves (~ 9 arcsec) to date on HgI2 as a result of the resolution of the instrument (~ 6 arcsec). Raman spectroscopy was used collaboratively to confirm little residual stress in the crystals. We developed a growth rate ratio (chi) and show this geometric model used to describe crystal shape and regions of <100> and <110> growth. Optical characterization of X-defects are presented and discussed. Further the influence of crystallographic defects and strain on radiation detector performance are discussed.
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