A series of In₂O₃ thin films, ranging from X-ray diffraction amorphous to highly crystalline, were grown on amorphous silica substrates using pulsed laser deposition by varying the film growth temperature. The amorphous-to-crystalline transition and the structure of amorphous In₂O₃ were investigated by grazing angle X-ray diffraction (GIXRD), Hall transport measurement, high resolution transmission electron microscopy (HRTEM), electron diffraction, extended X-ray absorption fine structure (EXAFS), and ab initio molecular dynamics (MD) liquid-quench simulation. On the basis of excellent agreement between the EXAFS and MD results, a model of the amorphous oxide structure as a network of InO_x polyhedra was constructed. Mechanisms for the transport properties observed in the crystalline, amorphous-to-crystalline, and amorphous deposition regions are presented, highlighting a unique structure–property relationship.

We report the in-plane electron transport in the MXenes (i.e., within the MXene layers) as a function of composition using the density-functional tight-binding method, in conjunction with the non-equilibrium Green’s functions technique. Our study reveals that all MXene compositions have a linear relationship between current and voltage at lower potentials, indicating their metallic character. However, the magnitude of the current at a given voltage (conductivity) has different trends among different compositions. For example, MXenes without any surface terminations (Ti3C2) exhibit higher conductivity compared to MXenes with surface functionalization. Among the MXenes with –O and –OH termination, those with –O surface termination have lower conductivity than the ones with –OH surface terminations. Interestingly, conductivity changes with the ratio of –O and –OH on the MXene surface. Our calculated I–V curves and their conductivities correlate well with transmission functions and the electronic density of states around the Fermi level. The surface composition-dependent conductivity of the MXenes provides a path to tune the in-plane conductivity for enhanced pseudocapacitive performance.

Structural properties of amorphous In-based oxides, $\mathrm{In}-X-\mathrm{O}$ with $X=\text{Zn}$, Ga, Sn, or Ge, are investigated using ab initio molecular dynamics liquid-quench simulations. The results reveal that indium retains its average coordination of 5.0 upon 20% $X$ fractional substitution for In, whereas $X$ cations satisfy their natural coordination with oxygen atoms. This finding suggests that the carrier generation is primarily governed by In atoms, in accord with the observed carrier concentration in amorphous In-O and $\mathrm{In}-X-\mathrm{O}$. At the same time, the presence of $X$ affects the number of six-coordinated In atoms as well as the oxygen sharing between the ${\mathrm{InO}}_6$ polyhedra. Based on the obtained interconnectivity and spatial distribution of the ${\mathrm{InO}}_6$ and ${X\mathrm{O}}_x$ polyhedra in amorphous $\mathrm{In}-X-\mathrm{O}$, composition-dependent structural models of the amorphous oxides are derived. The results help explain our Hall mobility measurements in $\mathrm{In}-X-\mathrm{O}$ thin films grown by pulsed-laser deposition and highlight the importance of long-range structural correlations in the formation of amorphous oxides and their transport properties.

The power conversion efficiency of perovskite solar cells can be significantly improved if recombination losses and hysteresis effects, often caused by the presence of structural and chemical defects present at grain boundaries and interfaces, can be minimized during the processing of photoactive layers. As a crucial first step to address this issue, we performed density functional theory calculations to evaluate the electronic structure of the energetically favored (110) perovskite surface in the presence of the widely reported IPb antisite defects. Our calculations indicate that the nature of trap states formed is different for the perovskite surface with exposed methylammonium (MAI) and lead iodide (PbI2) terminating groups. While, in MAI terminated surfaces, IPb antisite defects lead to shallow states close to the valence band, both deep and shallow states are created in the bandgap region in the PbI2 terminated surface. Furthermore, we determined contribution from individual atoms to the trap states and inferred that the trap states originate from the clusters of iodine atoms that are formed near the defect site. The exact nature of the defect state is strongly correlated with the atomic structure of these clusters and can be potentially tuned by controlling the processing conditions of the perovskite film.