The general objective of this proposal is to develop enabling technology for a new type of radiation detectors for charged particles, neutrons, x-ray and gamma rays and characterized by light weight, compact size, portability, room temperature operation, superior radiation resistance and two orders of magnitude lower cost compared with existing crystalline germanium and silicon detectors. The specific objective is to fabricate stacked, monolithic, multijunction, thin-film amorphous silicon alloy (a-si) devices deposited on thin, flexible, stainless steel foils by existing commercial processes used in the production of solar cells. The devices will utilize state-of-the art materials in combination will advanced device structures. Use of textured substrates, deposition of multijunction semiconducting a-si layers by glow discharge techniques, deposition of front electrodes, patterning and fabrication of radiation sensor structures, and testing them for dark current and for detection of incident charged particle and neutron, x-ray and gamma radiation.