arXiv subjects

James G. Champlain

Publications and source records attributed to James G. Champlain.

3 recordsLinked to original sources

arXiv2025

Enhanced Permittivity in Wurtzite ScAlN through Nanoscale Sc Clustering

ScN alloyed AlN (ScxAl1-xN, ScAlN) is a wurtzite semiconductor with attractive ferroelectric, dielectric, piezoelectric, and optical properties. Here, we show that ScAlN films (with x spanning 0.18 to 0.36) contain nanoscale Sc-rich clusters which maintain the wurtzite crystal structure. While both molecular beam epitaxy (MBE) and sputter deposited Sc0.3Al0.7N films show Sc clustering, the degree of clustering is significantly stronger for the MBE-grown film, offering an explanation for some of the discrepancies between MBE-grown and sputtered films reported in the literature. Moreover, the MBE-grown Sc0.3Al0.7N film exhibits a dispersive and anomalously large dielectric permittivity, roughly double that of sputtered Sc0.3Al0.7N. We attribute this result to the Sc-rich clusters locally reaching x ~ 0.5 and approaching the predicted ferroelectric-to-paraelectric phase transition, resulting in a giant (local) enhancement in permittivity. The Sc-rich clusters should similarly affect the piezoelectric, optical, and ferroelectric responses, suggesting cluster-engineering as a means to tailor ScAlNs functional properties.

cond-mat.mtrl-sci↗

arXiv2025

Modeling Practical Capacitive Structures for Electronic and Dielectric Property Extraction and Analysis

A method for modeling the full steady-state and small-signal behavior of practical capacitive structures, such as metal-insulator-metal capacitors, diodes, and transistors, is presented. Simple lumped element models fail to properly represent the behavior of most practical structures, resulting in incorrect electronic material property extraction and evaluation. The methodology and model presented in this paper properly characterizes practical structures and can be employed to more accurately understand and evaluate experimental results, extract various electronic and dielectric properties of the constituent materials, and predict possible behavior of new structures and materials. The impact of dielectric properties (e.g., real versus complex permittivity, conductance, Cole-Cole dielectric response) and geometry on observed behavior of practical structures, especially with regard to extracting correct property values, is discussed.

cond-mat.mtrl-sci↗

arXiv2025

Strongly dispersive dielectric properties of high-ScN-fraction ScAlN deposited by molecular beam epitaxy

We present a comprehensive study of dielectric properties including complex permittivity, loss, and leakage of high-ScN-fraction ScAlN thin films grown using molecular beam epitaxy (MBE). Dielectric spectroscopy is carried out on high-ScN-fraction (30%-40% ScN fraction) samples from 20 Hz to 10 GHz. We find that real permittivity ε' increases significantly with increasing ScN fraction; a trend confirmed by density functional theory. Further, ε' is strongly dispersive with frequency and increasing ScN fraction, with values for Sc0.4Al0.6N varying from 150 down to 60 with increasing frequency. Loss, dispersion, and DC leakage current correspondingly increase with ScN fraction. The high ε' and strongly dispersive behavior in MBE ScAlN are not observed in a sputter-deposited ScAlN control with a similar ScN fraction, highlighting fundamental differences between films produced by the two deposition methods. Microscopy and spectroscopy analyses are carried out on MBE- and sputter-deposited samples to compare microstructure, alloy, and dopant concentration.

cond-mat.mtrl-sci↗