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The proposed X-ray spatial light modulator (SLM) concept is based on the difference of X-ray scattering from amorphous and crystalline regions of phase change materials (PCMs) such as Ge₂Sb₂Te₅(GST). In our X-ray SLM design, the“on” and“off” states correspond to a patterned and homogeneous state of a GST thin film, respectively. The patterned state is obtained by exposing the homogeneous film to laser pulses. In this paper, we present patterning results in GST thin films characterized by microwave impedance microscopy and X-ray small-angle scattering at the Stanford Synchrotron Radiation Lightsource.

Understanding the formation chemistry of metal halide perovskites is key to optimizing processing conditions and realizing enhanced optoelectronic properties. Here, we reveal the structure of the crystalline precursor in the formation of methylammonium lead iodide (MAPbI₃) from the single-step deposition of lead chloride and three equivalents of methylammonium iodide (PbCl₂ + 3MAI) (MA = CH₃NH₃). The as-spun film consists of crystalline MA₂PbI₃Cl, which is composed of one-dimensional chains of lead halide octahedra, coexisting with disordered MACl. We show that the transformation of precursor into perovskite is not favored in the presence of MACl, and thus the gradual evaporation of MACl acts as a self-regulating mechanism to slow the conversion. We propose the stable precursor phase enables dense film coverage and the slow transformation may lead to improved crystal quality. This enhanced chemical understanding is paramount for the rational control of film deposition and the fabrication of superior optoelectronic devices.