Organisms in nature can alter the short-range order of an amorphous precursor phase, thereby controlling the resulting crystalline structure. This phenomenon inspired an investigation of the effect of modifying the short-range order within the amorphous phase of a selected material. Amorphous thin films of aluminum oxide deposited by the atomic layer deposition method were found to vary structurally as a function of size. Thinner films, as predicted and also confirmed by atomistic simulations, exhibited more 4 coordinated alumina sites. These atomistic alterations were expected to change the amorphous thin film average density. The density indeed varied with the alumina layer thickness, and the measured effect was even stronger than predicted theoretically. This effect is explained in terms of the deposition process, where each newly deposited layer is a new surface layer that remembers its structure, resulting in thin films of substantially lower density.
The two-dimensional electron system found between LaAlO3 and SrTiO3 hosts a variety of physical phenomena that can be tuned through external stimuli. This allows for electronic devices controlling magnetism, spin-orbit coupling, and superconductivity. Controlling the electron density by varying donor concentrations and using electrostatic gating are convenient handles to modify the electronic properties, but the impact on the microscopic scale, particularly of the former, remains underexplored. Here, we image the current distribution at 4.2 K in amorphous-LaAlO3/SrTiO3 using scanning supercond…
From Amorphous to Amorphous-Crystalline Mixed-Phase Boron Nitride: Evolution of the Thermal and Elastic Properties
Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST（加泰罗尼亚纳米科学与纳米技术研究所）；Faculty of Physics, Autonomous University of Barcelona（巴塞罗那自治大学物理系）；Universite Claude Bernard Lyon 1, CNRS, LMI, UMR 5615（里昂第一大学）；Faculty of Physics and Astronomy, Adam Mickiewicz University（亚当密茨凯维奇大学物理与天文学院）；International Iberian Nanotechnology Laboratory（伊比利亚纳米技术国际实验室）；ICREA（加泰罗尼亚高级研究院）
Evolution of the structure of amorphous ice - from low-density amorphous (LDA) through high-density amorphous (HDA) to very high-density amorphous (VHDA) ice
We consider the two-dimensional bimolecular recombination of charge carriers in amorphous organic semiconductors having the lamellar structure. We calculate the dependence of the effective recombination rate constant on the carrier density taking into account the correlated nature of the energetic disorder typical for organic semiconductors. Resulting recombination kinetics demonstrates a very rich variety of behaviors depending on the correlation properties of the particular semiconductor and relevant charge density range.
Boron-assisted synthesis of compositionally complex amorphous oxides via short-range-order-constrained generative design
Key Laboratory of Material Simulation Methods and Software of Ministry of Education, College of Physics, Jilin University（吉林大学物理学院教育部材料模拟方法与软件重点实验室）；Aiiso Yufeng Li Family Department of Chemical and Nano Engineering, University of California, San Diego（加州大学圣地亚哥分校爱思唯尔俞峰李家族化学与纳米工程系）；College of Chemistry and Molecular Engineering, Peking University（北京大学化学与分子工程学院）；Institute of Molecular Engineering Plus, College of Chemistry, Fuzhou University（福州大学化学学院分子工程+研究院）；Institute of Modern Physics, Fudan University（复旦大学现代物质结构研究所）；Program in Materials Science and Engineering, University of California, San Diego（加州大学圣地亚哥分校材料科学与工程项目）；Center for Renewable Energy and Storage Technologies, Physical Science and Engineering Division, King Abdullah University of Science and Technology（阿卜杜拉国王科技大学物理科学与工程学院可再生能源与储能技术中心）；Department of Computer Science and Engineering, University of California, San Diego（加州大学圣地亚哥分校计算机科学与工程系）
The nanostructure of hydrogenated amorphous silicon (a Si:H) is studied by a combination of small-angle X-ray (SAXS) and neutron scattering (SANS) with a spatial resolution of 0.8 nm. The a-Si:H materials were deposited using a range of widely varied conditions and are representative for this class of materials. We identify two different phases which are embedded in the a-Si:H matrix and quantified both according to their scattering cross-sections. First, 1.2 nm sized voids (multivacancies with more than 10 missing atoms) which form a superlattice with 1.6 nm void-to-void distance are detected…
Enhancing Gate Control and Mitigating Short Channel Effects in 20-50 nm Channel Length Amorphous Oxide Thin Film Transistors
Chandra Family Department of Electrical and Computer Engineering, The University of Texas at Austin（德克萨斯大学奥斯汀分校陈氏电气与计算机工程系）；Microelectronics Research Center, The University of Texas at Austin（德克萨斯大学奥斯汀分校微电子研究中心）
We developed a capacitor type heat flow switching device, in which electron thermal conductivity of the electrodes is actively controlled through the carrier concentration varied by an applied bias voltage. The devices consist of an amorphous p-type Si-Ge-Au alloy layer, an amorphous SiO$_2$ as the dielectric layer, and a n-type Si substrate. Both amorphous materials are characterized by very low lattice thermal conductivity, less than 1 Wm-1K-1. The Si-Ge-Au amorphous layer with 40 nm in thickness was deposited by means of molecular beam deposition technique on the 100 nm thick SiO$_2$ layer …
Disordered hyperuniformity (DHU) is a recently proposed new state of matter, which has been observed in a variety of classical and quantum many-body systems. DHU systems are characterized by vanishing infinite-wavelength density fluctuations and are endowed with unique novel physical properties. Here we report the first discovery of disordered hyperuniformity in atomic-scale 2D materials, i.e., amorphous silica composed of a single layer of atoms, based on spectral-density analysis of high-resolution transmission electron microscope images. Subsequent simulations suggest that the observed DHU …
High quality stoichiometric magnetite (Fe3O4) films grown by infrared pulsed laser deposition (IR-PLD) on different surfaces were investigated in order to study the influence of the substrate, orientation, and thickness on their magnetic behavior. Different single crystal (001)-oriented substrates, i.e., SrTiO3(001), MgAl2O4(001) and MgO(001), have been used for the preparation of epitaxial Fe3O4(001) films. By comparison, polycrystalline magnetite films were obtained on both single crystal Al2O3(0001) and amorphous Si/SiO2 substrates. The thickness has been varied between 50 - 400 nm. All fil…
Planar flow casting (PFC) is a method that can be used to make thin, long, and wide metallic alloy foils by extruding molten liquid through a thin and wide nozzle and immediately quenching on a moving roller. The quenching rates are high enough that amorphous metallic glasses may be formed which have many desirable properties for a wide variety of applications. This paper reviews how PFC processes were developed, examines the typical operability range of PFC, and reviews the defects that commonly form. The geometrical similarities between PFC and slot coating process are apparent, and this pap…
The influence of variable-amplitude loading on the potential energy and mechanical properties of amorphous materials is investigated using molecular dynamics simulations. We study a binary mixture that is either rapidly or slowly cooled across the glass transition temperature and then subjected to a sequence of shear cycles with strain amplitudes above and below the yielding strain. It was found that well annealed glasses can be rejuvenated by small-amplitude loading if the strain amplitude is occasionally increased above the critical value. By contrast, poorly annealed glasses are relocated t…
Ion-beam irradiation of an amorphizable material such as Si or Ge may lead to spontaneous pattern formation beyond some critical angle of the beam versus the surface. It is known from experimental results that this critical angle varies according to beam energy, ion species and target material. However, most prevailing theoretical analyses predict a critical angle of $45^{\circ}$ independent of energy, ion and target, disagreeing with experiment. In this second part of a set of papers, we consider the influence of the relationship between the upper and lower interfaces of the amorphous thin fi…
The objective of this work was to study the RF sputtering process parameters optimisation for deposition of Silicon Nitride thin films. The process parameters chosen to be varied were deposition power, deposition duration, flow rate of argon and flow rate of nitrogen. The parameters were varied at three levels according to Taguchi L9 orthogonal array. Surface topology, film composition, coating thickness, coating resistivity and refractive index were determined using SEM, XRD, profilometer, Semiconductor device analyser and UV spectrometer respectively. The measured film thickness values range…
This paper reports on the deposition of amorphous and crystalline thin films of Ga2O3 by reactive pulsed direct current magnetron sputtering from a liquid gallium target onto fused (f-) quartz and c plane (c-) sapphire substrates, where the temperature of the substrate is varied from room temperature (RT) to 800°C. The deposition rate (up to 37 nm/min at RT on f-quartz and 5 nm/min at 800°C on c-sapphire) is two to five times higher than the data given in the literature for radio frequency sputtering. Deposited onto unheated substrates, the films are X-ray amorphous. Well-defined X-ray diffrac…
We investigate the use of ultrafast lasers exposure to induce localized crystallization and elemental redistribution in amorphous dielectric multi-layers, composed of alternating Si3N4and SiO2layers of sub-micron thickness. Specifically,we report on the occurrence of a laser-induced elemental intermixing process and on the presence of silicon nanocrystals clusters localized within the multi-layers structure. The spatial distribution of these clusters goes significantly beyond the zone under direct laser exposure providing evidences of energy being channeled transversely to the laser propagatio…
Conventional fabrication methods to produce graphene are cumbersome, expensive and are not ecology friendly. This is due to the fact that a large volume of raw materials requires a large number of acids and alkalis, which in turn requires special disposal. Therefore, it is necessary to develop new technologies or refine existing technologies for the production of graphene and create new ecology-safe and effective methods to produce graphene. Here, we utilized the physical dispergation to extract graphene films from natural mineral shungite rock. We studied the structure of shungite via Raman s…
