arXiv subjects

Lisa M. Porter

Publications and source records attributed to Lisa M. Porter.

2 recordsLinked to original sources

arXiv2026

Kinetics studies on $\kappa$ to $\beta$-Ga$_2$O$_3$ phase transformations via in-situ high temperature X-ray diffraction

The kinetics of the $\kappa$ to $\beta$-Ga$_2$O$_3$ phase transformation were investigated in five batches of nominally phase-pure $\kappa$-Ga2O3 thin films heteroepitaxially grown on c-plane sapphire, with film thickness ranging from 700 to 1100 nm, using in-situ high-temperature X-ray diffraction. Phase fractions were quantitatively extracted through modified Rietveld refinement that accounts for preferred orientation, and the transformation kinetics were analyzed using the Johnson-Mehl-Avrami-Kolmogorov (JMAK) model. The applicability of the JMAK model to thin-film materials was evaluated and its lower and upper bounds for thin films and bulk materials were established. Based on this analysis, a method specifically suited for thin-film kinetic studies was developed and yielded reproducible and robust results across all five sample batches. The results indicate that the $\kappa$ to $\beta$ phase transformation in ~700-1100 nm films is best described as an interface-controlled, site-saturated nucleation with thickness-limited or effectively two-dimensional growth.

cond-mat.mtrl-sci↗

arXiv2026

First-Principles Study of Mg-Induced Phase Stabilization in Ga$_2$O$_3$ polymorphs

In this study, we investigate the effect of Mg incorporation on the relative phase stability of the four primary Ga$_2$O$_3$ polymorphs using density functional theory (DFT) calculations, with the goal of rationalizing experimental observations suggesting that diffusion from MgAl$_2$O$_4$ substrates contributes to relative stabilization of the $\gamma$ phase. Mg incorporation is modeled up to 25% of Ga sites within supercells derived from fully relaxed unit cells of each polymorph. Our results show that while $\beta$-Ga$_2$O$_3$ remains the thermodynamically most stable phase, the enthalpic differences between polymorphs decrease with increasing Mg content. The inherently disordered $\gamma$ phase, with its high configurational entropy, becomes less energetically unfavorable under Mg substitution, suggesting that entropy-driven stabilization may facilitate its formation under high-temperature and/or nonequilibrium growth conditions such as those previously reported. These findings provide a thermodynamic rationale for the experimental observation of the $\gamma$ phase during epitaxial growth on MgAl$_2$O$_4$ spinel substrates.

cond-mat.mtrl-sci↗