OptoGPT: A foundation model for inverse design in optical multilayer thin film structures

Optical multilayer thin film structures have been widely used in numerous photonic applications.However,existing inverse design methods have many drawbacks because they either fail to quickly adapt to different design targets,or are difficult to suit for different types of structures,e.g.,designing for different materials at each layer.These methods also cannot accommodate versatile design situations under different angles and polarizations.In addition,how to benefit practical fabrications and manufacturing has not been extensively considered yet.In this work,we introduce OptoGPT(Opto Generative Pretrained Transformer),a decoder-only transformer,to solve all these drawbacks and issues simultaneously.

Evolution of Magnetic Domain Structure in a YIG Thin Film

The evolution of a magnetic domain structure induced by temperature and magnetic field is reported in silicon- doped yttrium iron garnet （YIG） films with perpendicular anisotropy. During a cooling-down procedure from 300K to 7K, a 20% change in the domain width is observed, with the long tails of the stripes being shortened and the twisting stripes being straightened. Under the influence of the stray field of a barium ferrite, the garnet presents an interesting domain structure, which shows an appearance of branching protrusions. The intrinsic mechanisms in these two processes are also discussed.

Coacervate Structures of CdI_2 Thin Film Grown during Phase Transformation

The microstructure of CdI2 thin film grown during vapor-phase deposition was investigated by scanning electron microscopy (SEM). The thin film deposited on Si crystal consists of numerous sunflower-like aggregates. These aggregates display well self-assembly characteristics. The size of Sunflower-like aggregates is between 12 and 44 μm. Each sunflower-like aggregate is surrounded with many adjacent wings-'petals'. The structure of central region of the 'sunflower' is obviously difFerent from that of the 'petal'. Electron spectroscopy for chemical analysis (ESCA) was employed in determining the chemical valence of the thin film. Self-organization efFect is used to explain the coring growth process of CdI2 thin film

Structural and Magnetic Properties of Co2MnSi Thin Film with a Low Damping Constant

Co2MnSi thin films are made by magnetron sputtering onto MgO （001） substrates. The crystalline quality is improved by increasing depositing temperature and/or annealing temperature. The sample deposited at 550℃ and subsequently annealed at 550℃ （sample I） exhibits a pseudo-epitaxial growth with partially ordered L21 phase. Sample I shows a four-fold magnetic anisotropy, in addition to a relatively weak uniaxial anisotropy. The Gilbert damping factor of sample I is smaller than 0.001, much smaller than reported ones. The possible reasons responsible for the small Gilbert damping factor are discussed, including weak spin-orbit coupling, small density of states at Fermi level, and so on.

Prediction and Regulation of Delamination at Flexible Film/Finite-Thickness-Substrate Structure Interfaces

Regulating the surface instability of thin film/substrate structures has been successfully applied to prepare new ductile electronic devices.However,such electronic devices need to be subjected to external loads during operation,which can easily induce delamination of the thin-film electronic device from the substrate.This study aims to investigate the instability characteristics of hard films on flexible substrate surfaces from theoretical analysis and numerical simulation perspectives.Considering finite-thickness substrates,this paper establishes theoretical models for pure bending,bent wrinkle,partial delamination,and total delamination buckling of film/substrate structures based on the nonlinear Euler–Bernoulli beam theory and the principle of minimum energy;then the effects of material and geometric parameters of the structure,interfacial adhesion strength,and pre-strain on the evolutionary path of the four patterns are discussed.The study results show that:the greater Young’s modulus of the substrate is,the larger the parameter region where partial delamination of the film/substrate structure occurs,and the smaller the parameter region where bent wrinkle occurs.By varying Young’s modulus,thickness of the film and substrate,interfacial adhesion coefficient,and pre-strain,the buckling pattern of the structure can be predicted and regulated.The parametric design intervals for each pattern are summarized in the phase diagram.The results of this paper provide theoretical support for the design and reliability evaluation of flexible electronic devices.

Water and nutrient recovery from urine:A lead up trail using nano-structured In_(2)S_(3)photo electrodes

Developments of economic systems are critical for bio-regenerative life support systems in manned space missions.In this work we report on the feasibility of using two direct sunlight powered processes sequentially for the recovery of water and nutrients from urine.The work presents experimental evidence on nutrient and water recovery achieved using the proto-type designed and developed.We report the design and testing of a solar still which would serve on the nutrient recovery front.The cooled condensate from the solar still is fed into a solar powered electrolysis unit where nano-structured indium sulphide(In_(2)S_(3))thin films coated over fluorine doped tin oxide(SnO_(2):F)substrate serve as one of the working electrodes.The electrolysis takes place in the absence of an electrolyte which manifests as a technical achievement of our work.Our results show that the COD level in the recycled water is very low.The In_(2)S_(3)photo-electrodes are stable without any physical damage after the process.

Light output improvement of GaN-based light-emitting diodes grown on Si (111) by a via-thin-film structure

This work reports the fabrication of via-thin-film light-emitting diode （via-TF-LED） to improve the light output power （LOP） of blue/white GaN-based LEDs grown on Si （111） substrates. The as-fabricated via-TF-LEDs were featured with a roughened n-GaN surface and the p-GaN surface bonded to a wafer carrier with a silver-based reflective electrode, together with an array of embedded n-type via pillar metal contact from the p-GaN surface etched through the multiple-quantum-wells （MQWs） into the n-GaN layer. When operated at 350 mA, the via-TF- LED gave an enhanced blue LOP by 7.8% and over 3.5 times as compared to the vertical thin-film LED （TF-LED） and the conventional lateral structure LED （LS-LED）. After covering with yellow phosphor that converts some blue photons into yellow light, the via-TF-LED emitted an enhanced white luminous flux by 13.5% and over 5 times, as compared with the white TF-LED and the white LS-LED, respectively. The significant LOP improve- ment of the via-TF-LED was attributed to the elimination of light absorption by the Si （111） epitaxial substrate and the finger-like n-electrodes on the roughened emitting surface.

Preface: Advanced Thin Film Developments and Nano Structures

In this special issue, we invited a few leading materials researchers to present topics in thin films, coatings, and nano structures. Readers will find most recent developments in topics, including recent advances in hard, tough, and low friction nanocomposite coatings; thin films for coating nanomaterials; electroless plating of silver thin films on porous Al2O3 substrate; CrN/Nano Cr interlayer coatings; nano-structured carbide derived carbon （CDC） films and their tribology; predicting interdiffusion in high-temperature coatings; gallium-catalyzed silica nanowire growth; and corrosion protection properties of organofunctional silanes. Authors are from both national laboratories and academia.

Laser direct writing pattern structures on AgInSbTe phase change thin film

Different pattern structures are obtained on the AglnSbTe （AIST） phase change film as induced by laser beam. Atomic force microscopy （AFM） was used to observe and analyze the different pattern structures. The AFM photos clearly show the gradually changing process of pattern structures induced by different threshold effects, such as crystallization threshold, microbump threshold, melting threshold, and ablation threshold. The analysis indicates that the AIST material is very effective in the fabrication of pattern structures and can offer relevant guidance for application of the material in the future.

Physical Parameter Variation Analysis on the Performance Characteristics of Nano DG-MOSFETs

DG-MOSFETs are the most widely explored device architectures for nano-scale CMOS circuit design in sub-50 nm due to the improved subthreshold slope and the reduced leakage power compared to bulk MOSFETs. In thin-film (tsi < 10 nm) DG-MOS structures, charge carriers are affected by tsi- induced quantum confinement along with the confinement caused by a very high electric field at the interface. Therefore, quantum confinement effects on the device characteristics are also quite important and it needs to be incorporated along with short channel effects for nano-scale circuit design. In this paper, we analyzed a DG-MOSFET structure at the 20 nm technology node incorporating quantum confinement effects and various short channel effects. The effect of physical parameter variations on performance characteristics of the device such as threshold voltage, subthreshold slope, ION - IOFF ratio, DIBL, etc. has been investigated and plotted through extensive TCAD simulations. The physical parameters considered in this paper are operating temperature (Top), channel doping concentration (Nc), gate oxide thickness (tox) and Silicon film thickness (tsi). It was observed that quantum confinement of charge carriers significantly affected the performance characteristics (mostly the subthreshold characteristics) of the device and therefore, it cannot be ignored in the subthreshold region-based circuit design like in many previous research works. The ATLASTM device simulator has been used in this paper to perform simulation and parameter extraction. The TCAD analysis presented in the manuscript can be incorporated for device modeling and device matching. It can be used to illustrate exact device behavior and for proper device control.