Absorption line broadening in atomic beams produced in a molecular beam epitaxy environment.

Tunable diode laser absorption spectroscopy (TDLAS) is used to measure the 6s S-5d6p D absorption line profile of a Ba atomic beam produced in a molecular beam epitaxy (MBE) reactor. Despite the noisy MBE environment, a signal-to-noise ratio up to 100 is obtained thanks to a thorough optimization of the measurement setup. A model that realistically describes this absorption profile is presented, taking into account the angular distribution of atomic concentration in the atomic beam as well as the reactor and setup geometry.

Integration of epitaxial LiNbOthin films with silicon technology.

Development of bulk acoustic wave filters with ultra-wide pass bands and operating at high frequencies for 5and 6generation telecommunication applications and micro-scale actuators, energy harvesters and sensors requires lead-free piezoelectric thin films with high electromechanical coupling and compatible with Si technology. In this paper, the epitaxial growth of 36°Y-X and 30°X-Y LiNbOfilms by direct liquid injection chemical vapour deposition on Si substrates by using epitaxial SrTiOlayers, grown by molecular beam epitaxy, has been demonstrated. The stability of the interfaces and chemical interactions between SrTiO, LiNbOand Si were studied experimentally and by thermodynamical calculations.

Ferroelectric HfZrO films with improved endurance obtained through low temperature epitaxial growth on seed layers.

Crystallization temperature is a critical parameter in the stabilization of the metastable ferroelectric phase of HfO. The optimal crystallization temperature used for polycrystalline films is too low to grow epitaxial films. We have developed a new growth strategy, based on the use of an ultrathin seed layer, to obtain high-quality epitaxial films of orthorhombic HfZrO at a lower temperature.

Integration of LiTiO Crystalline Films on Silicon Toward High-Rate Performance Lithionic Devices.

The growth of crystalline Li-based oxide thin films on silicon substrates is essential for the integration of next-generation solid-state lithionic and electronic devices including on-chip microbatteries, memristors, and sensors. However, growing crystalline oxides directly on silicon typically requires high temperatures and oxygen partial pressures, which leads to the formation of undesired chemical species at the interface compromising the crystal quality of the films. In this work, we employ a 2 nm gamma-alumina (γ-AlO) buffer layer on Si substrates in order to grow crystalline thin films of LiTiO (LTO), a well-known active material for lithium-ion batteries.

Tunable optical anisotropy in epitaxial phase-change VO thin films.

We theoretically and experimentally demonstrate a strong and tunable optical anisotropy in epitaxially-grown VO thin films. Using a combination of temperature-dependent X-ray diffraction, spectroscopic ellipsometry measurements and first-principle calculations, we reveal that these VO thin films present an ultra-large birefringence (Δ > 0.9).

Impact of La Concentration on Ferroelectricity of La-Doped HfO Epitaxial Thin Films.

Epitaxial thin films of HfO doped with La have been grown on SrTiO(001) and Si(001), and the impact of the La concentration on the stabilization of the ferroelectric phase has been determined. Films with 2-5 at. % La doping present the least amount of paraelectric monoclinic and cubic phases and exhibit the highest polarization, having a remanent polarization above 20 μC/cm.

Electric and Mechanical Switching of Ferroelectric and Resistive States in Semiconducting BaTiO Films on Silicon.

Materials that can couple electrical and mechanical properties constitute a key element of smart actuators, energy harvesters, or many sensing devices. Within this class, functional oxides display specific mesoscale responses which often result in great sensitivity to small external stimuli. Here, a novel combination of molecular beam epitaxy and a water-based chemical-solution method is used for the design of mechanically controlled multilevel device integrated on silicon.

Thermoelectric La-doped SrTiO epitaxial layers with single-crystal quality: from nano to micrometers.

High-quality thermoelectric LaSrTiO (LSTO) films, with thicknesses ranging from 20 nm to 0.7 μm, have been epitaxially grown on SrTiO(001) substrates by enhanced solid-source oxide molecular-beam epitaxy. All films are atomically flat (with rms roughness < 0.

Continuous-wave operation of monolithically grown 1.5-microm optically pumped vertical-external-cavity surface-emitting lasers.

Continuous-wave operation, to as high as 7 degrees C, of 1.5-microm optically pumped vertical-external-cavity surface-emitting lasers is reported. The epitaxial structure, monolithically grown on InP by metal-organic chemical vapor deposition, consists of an InAlAs/GaInAlAs Bragg reflector, an InGaAs/InGaAsP active region, and an InP capping layer.