2021 New's Items

Directed assembly of layered perovskite heterostructures as single crystals

M. L. Aubrey
A. S. Valdes
M. R. Filip
B. A. Connor
K. P. Lindquist
J. B. Neaton
H. I. Karunadasa
2021

The precise stacking of different two-dimensional (2D) structures such as graphene and MoS2 has reinvigorated the field of 2D materials, revealing exotic phenomena at their interfaces1,...

Software for the frontiers of quantum chemistry: An overview of developments in the Q-Chem 5 package

E. Epifanovsky
J. B. Neaton
K. B. Whaley
A. I. Krylov
2021

This article summarizes technical advances contained in the fifth major release of the Q-Chem quantum chemistry program package, covering developments since 2015. A comprehensive library of exchange–correlation functionals, along with a suite of correlated many-body methods, continues to be a hallmark of the Q-Chem software. The many-body methods include novel variants of both coupled-cluster and configuration-interaction approaches along with methods based on the algebraic diagrammatic construction and variational reduced density-matrix methods. Methods highlighted in Q-Chem 5...

Band Edge Energy Tuning through Electronic Character Hybridization in Ternary Metal Vanadates

M. H. Richter
E. A. Peterson
L. Zhou
A. A. Shinde
P. F. Newhouse
Q. Yan
S. W. Fackler
J. Yano
J. K. Cooper
K. A. Persson
J. B. Neaton
J. M. Gregoire
2021

In the search for photoanode materials with band gaps suitable for utilization in solar fuel generation, approximately 1.2–2.8 eV, theory-guided experiments have identified a variety of materials that meet the band gap requirements and exhibit operational stability in harsh photoelectrochemical environments. In particular, M-V-O compounds (M is a transition metal or main group element) with VO4 structural motifs were predicted to show a remarkably wide range of band energetics (>3 eV variation in the energy of valence band maximum) and characteristics,...

Exploring the Pb1−xSrxHfO3 System and Potential for High Capacitive Energy Storage Density and Efficiency

M. Acharya
E. Banyas
M. Ramesh
Y. Jiang
A. Fernandez
A. Dasgupta
H. Ling
B. Hanrahan
K. Persson
J. B. Neaton
L. W. Martin
2021

The hafnate perovskites PbHfO3 (antiferroelectric) and SrHfO3 (“potential” ferroelectric) are studied as epitaxial thin films on SrTiO3 (001) substrates with the added opportunity of observing a morphotropic phase boundary (MPB) in the Pb1−xSrxHfO3 system. The resulting (240)-oriented PbHfO3 (Pba2) films exhibited antiferroelectric switching with a saturation polarization ≈53 µC...

A wearable nutrition tracker

Zhao J
Nyein HY
Hou L
Lin Y
Bariya M
Ahn CH
Ji W
Fan Z
Javey A
2021

Nutrients are essential for the healthy development and proper maintenance of body functions in humans. For adequate nourishment, it is important to keep track of nutrients level in the body, apart from consuming sufficient nutrition that is in line with dietary guidelines. Sweat, which contains rich chemical information, is an attractive biofluid for routine non-invasive assessment of nutrient levels. Herein, a wearable sensor that can selectively measure vitamin C concentration in biofluids, including sweat, urine, and blood is developed. Detection through an electrochemical sensor...

Performance Limits of an Alternating Current Electroluminescent Device

Wang V
Zhao Y
Javey A
2021

The use of an alternating current (AC) voltage is a simple, versatile method of producing electroluminescence from generic emissive materials without the need for contact engineering. Recently, it was shown that AC-driven, capacitive electroluminescent devices with carbon nanotube network contacts can be used to generate and study electroluminescence from a variety of molecular materials emitting in the infrared-to-ultraviolet range. Here, performance trade-offs in these devices are studied through comprehensive device simulations and illustrative experiments, enhancing understanding...

Universal Inverse Scaling of Exciton–Exciton Annihilation Coefficient with Exciton Lifetime

Uddin SZ
Rabani E
Javey A
2021

Be it for essential everyday applications such as bright light-emitting devices or to achieve Bose–Einstein condensation, materials in which high densities of excitons recombine radiatively are crucially important. However, in all excitonic materials, exciton–exciton annihilation (EEA) becomes the dominant loss mechanism at high densities. Typically, a macroscopic parameter named EEA coefficient (CEEA) is used to compare EEA rates between materials at the same density; higher CEEA implies higher EEA rate. Here, we find that the...

A wearable patch for continuous analysis of thermoregulatory sweat at rest

Nyein HY
Bariya M
Tran B
Ahn CH
Brown BJ
Ji W
Davis N
Javey A
2021

The body naturally and continuously secretes sweat for thermoregulation during sedentary and routine activities at rates that can reflect underlying health conditions, including nerve damage, autonomic and metabolic disorders, and chronic stress. However, low secretion rates and evaporation pose challenges for collecting resting thermoregulatory sweat for non-invasive analysis of body physiology. Here we present wearable patches for continuous sweat monitoring at rest, using microfluidics to combat evaporation and enable selective monitoring of secretion rate. We integrate...

Tellurium Single‐Crystal Arrays by Low‐Temperature Evaporation and Crystallization

Zhao C
Batiz H
Yasar B
Kim H
Ji W
Scott MC
Chrzan DC
Javey A
2021

Thermally evaporated tellurium possesses an intriguing crystallization behavior, where an amorphous to crystalline phase transition happens at near-ambient temperature. However, a comprehensive understanding and delicate control of the crystallization process for the evaporated Te films is lacking. Here, the kinetics and dynamics of the crystallization of thermally evaporated Te films is visualized and modeled. Low-temperature processing of highly crystalline tellurium films with large grain size and preferred out-of-plane orientation ((100) plane parallel to the surface) is...

A Resonantly Driven, Electroluminescent Metal Oxide Semiconductor Capacitor with High Power Efficiency

Wang V
Javey A
2021

Electroluminescence can be generated from a wide variety of emissive materials using a simple, generic device structure. In such a device, emissive materials are deposited by various means on a metal oxide semiconductor capacitor structure across which alternating current voltage is applied. However, these devices suffer from low external efficiencies and require the application of high voltages, thus hindering their practical usage and raising questions about the possible efficiencies that can be achieved using alternating current driving schemes in which injection of bipolar...