Detector Grade Lead Monoxide (beta-PbO) Micro/Nano Ribbons with Extreme Aspect Ratio Grown by Vapour Phase

Lead oxide is a promising material for room temperature radiation detectors, thanks to its high density, high atomic number, and large band gap energy. In particular, it has been mainly studied for the realization of flat panel detectors [1]. For these applications, PbO is generally grown from the vapor phase and polycrystalline films are generally obtained. PbO exists in two different forms, i.e. tetragonal (?-PbO, red PbO, Litharge) and orthorhombic (?-PbO, yellow PbO, Massicot) phases, and the complexity of stoichiometry and phase strongly limits the growth of this material in form of single crystal structures. As a result, carrier transport properties of obtained films are usually poor, the reported ?? products range from 1E-9 to 1E-7 cm2/Vsec [1, 2]. Aim of this work has been the investigation of synthesis approaches to obtain high quality PbO structures. As solution growth methods resulted to be strongly affected by a poor stoichiometric control, vapour phase growth has been then exploited. Optimal results have been found by vapor approach evaporating Pb metal source in a oxygen low pressure atmosphere. In particular micro/nano wires, or better ribbons, of PbO with an extreme length-to-thickness aspect ratio (10000:1) have been obtained in a reproducible way. TEM analyses showed that single ?-PbO structures were obtained, practically dislocations free. The micro/nano structures have also been characterized by photoluminescence. Single micro/nano ribbons were contacted and resistivity larger than 1E12 ?cm was measured. Single ribbon X-ray detection was demonstrated. By fitting the Hecht equation a ?? value larger than 1E-5 cm2/Vsec was found, paving the possibility to exploit the ribbons for the realization of spectroscopic X-ray microdetectors.