Measurement of residual stress in a multi-layer semiconductor heterostructure by micro-Raman spectroscopy

Si-based multilayer structures are widely used in current microelectronics. During their preparation, some inhomogeneous residual stress is induced, resulting in competition between interface mismatching and surface energy and even leading to structure failure. This work presents a methodological study on the measurement of residual stress in a multi-layer semiconductor heterostructure. Scanning electron microscopy（SEM）, micro-Raman spectroscopy（MRS）, and transmission electron microscopy（TEM） were applied to measure the geometric parameters of the multilayer structure. The relationship between the Raman spectrum and the stress/strain on the [100] and [110] crystal orientations was determined to enable surface and crosssection residual stress analyses, respectively. Based on the Raman mapping results, the distribution of residual stress along the depth of the multi-layer heterostructure was successfully obtained.

Two-dimensional semiconductor heterostructures for photocatalytic CO_(2)conversion

The CO_(2)reduction into carbon-contained fuel via solar energy offers the powerful tools to realize the zero-emission carbon cycle.Owing to the intriguing features of the two-dimensional(2D)heterostructures,it is susceptible to modulate the electronic structure as well as the surface geometry for optimizing the photocatalytic CO_(2)reactivity.From this perspective,we surveyed the fundamental insights of 2D semiconductor heterostructures,involving the fabrication strategies and classification of the 2D semiconductor heterostructure.Also,we have detailly discussed the overview of 2D semiconductor heterostructure for optimizing CO_(2)photocatalytic influenced factors,including the solar energy utilization,photogenerated carriers separation,and redox reaction kinetics.Afterwards,we showed the significant advantages of 2D heterostructures in elevating CO_(2)photoreduction performance,focusing on activity,selectivity and photostability.By analyzing the limitations and developments,we ended by putting forward insights into the further researches about the CO_(2)photocatalysts and reactor design,even industrial applications.

Comparative coherence between layered and traditional semiconductors: unique opportunities for heterogeneous integration

As Moore’s law deteriorates,the research and development of new materials system are crucial for transitioning into the post Moore era.Traditional semiconductor materials,such as silicon,have served as the cornerstone of modern technologies for over half a century.This has been due to extensive research and engineering on new techniques to continuously enrich silicon-based materials system and,subsequently,to develop better performed silicon-based devices.Meanwhile,in the emerging post Moore era,layered semiconductor materials,such as transition metal dichalcogenides(TMDs),have garnered considerable research interest due to their unique electronic and optoelectronic properties,which hold great promise for powering the new era of next generation electronics.As a result,techniques for engineering the properties of layered semiconductors have expanded the possibilities of layered semiconductor-based devices.However,there remain significant limitations in the synthesis and engineering of layered semiconductors,impeding the utilization of layered semiconductor-based devices for mass applications.As a practical alternative,heterogeneous integration between layered and traditional semiconductors provides valuable opportunities to combine the distinctive properties of layered semiconductors with well-developed traditional semiconductors materials system.Here,we provide an overview of the comparative coherence between layered and traditional semiconductors,starting with TMDs as the representation of layered semiconductors.We highlight the meaningful opportunities presented by the heterogeneous integration of layered semiconductors with traditional semiconductors,representing an optimal strategy poised to propel the emerging semiconductor research community and chip industry towards unprecedented advancements in the coming decades.

Demonstration and operation of quantum harmonic oscillators in an AlGaAs–GaAs heterostructure

The quantum harmonic oscillator(QHO),one of the most important and ubiquitous model systems in quantum mechanics,features equally spaced energy levels or eigenstates.Here we present a new class of nearly ideal QHOs formed by hydrogenic substitutional dopants in an AlGaAs/GaAs heterostructure.On the basis of model calculations,we demonstrate that,when aδ-doping Si donor substitutes the Ga/Al lattice site close to AlGaAs/GaAs heterointerface,a hydrogenic Si QHO,characterized by a restoring Coulomb force producing square law harmonic potential,is formed.This gives rise to QHO states with energy spacing of~8–9 meV.We experimentally confirm this proposal by utilizing gate tuning and measuring QHO states using an aluminum single-electron transistor(SET).A sharp and fast oscillation with period of~7–8 mV appears in addition to the regular Coulomb blockade(CB)oscillation with much larger period,for positive gate biases above 0.5 V.The observation of fast oscillation and its behavior is quantitatively consistent with our theoretical result,manifesting the harmonic motion of electrons from the QHO.Our results might establish a general principle to design,construct and manipulate QHOs in semiconductor heterostructures,opening future possibilities for their quantum applications.

The structural and magnetic properties of Fe/(Ga,Mn)As heterostructures

Fe/（Ga,Mn）As heterostructures were fabricated by all molecular-beam epitaxy.Double-crystal X-ray diffraction and high-resolution cross-sectional transmission electron micrographs show that the Fe layer has a well ordered crystal orientation and an abrupt interface.The different magnetic behavior between the Fe layer and（Ga, Mn）As layer is observed by superconducting quantum interference device magnetometry.X-ray photoelectron spectroscopy measurements indicate no Fe_2As and Fe-Ga-As compounds,i.e.,no dead magnetic layer at the interface, which strongly affects the magnetic proximity and the polarization of the Mn ion in a thin（Ga,Mn）As region near the interface of the Fe/（Ga,Mn）As heterostructure.

Photocatalysis vs adsorption by metal oxide nanoparticles

Background:Metal oxide(MO)nanomaterials and related nanocomposites have been extensively studied for their potential use in water treatment.Because of their controlled morphologies,texture qualities,variable surface chemistry,distinct crystalline nature,high stability,and tunable band edges,MO nanostructured materials are highly selective towards deleting organic contaminants and heavy metal ions via adsorption and semiconductor photocatalysis.Metal-enhanced photocatalysis has recently received increasing interest,mainly due to the ability of the metal to directly or indirectly degrade pollutants.A diverse selection of MOs,with titanium dioxide(Ti O2),zinc oxide(Zn O),iron oxides(IO),and tungsten(W),as well as graphene-MOs nanocomposites with variable structure,crystalline,and morphological properties,offers a powerful platform for the growth of effective catalysts.Methods:The current work discusses novel advancements and potential for the removal of adsorptive and photocatalytic degradation of organic compounds(phenolic,pesticide molecules,dyes,and so on)as well as heavy metal ions using semiconductor materials.A photocatalyst based on a MO-scheme heterostructure can manage the appropriate conduction band(CB)and valence band(VB)locations,securing considerable redox aptitude.This review should be of interest to the broad readership dealing with applied and fundamental aspects of water treatments and material sciences.Various strategies including surface modification,plasmonic enhancement,and metal cocatalysts have been introduced to enhance photocatalytic performance.Significant findings:The current article discussed the significantly utilized synthesis strategies and mechanism of heterojunction photocatalysts using a Z-scheme.Furthermore,adsorption sections guarantee that mercury,chromium,cadmium,arsenic,and lead-based ions are successfully removed from polluted water via the adsorption route.Numerous characteristics,such as concentration,coexisting ions,p H,and kind of chemical have converged to comprehend the adsorption procedure.The technological challenges and future approaches are discussed to maximize the photocatalytic and adsorption efficacy and the reusability of MO-based nanomaterials for water security.

Interface structure and strain controlled Pt nanocrystals grown at side facet of MoS_(2)with critical size

The heterostructure of transition metal nanocrystal on two-dimensional(2D)materials exhibits unique physical and chemical properties through various interfacial interactions.It has been established that the atomic structure and strain in the vicinity of the interface determine the band structure and phonon modes of the nanocrystal,regulating the optical and electrical properties of such heterostructures.Hence,metal–support interfacial engineering is a demonstrated approach to acquiring desired properties of the nanocrystals.However,a fundamental understanding of the interfacial structures remains elusive and precise control of the interactions has yet achieved.Herein,we explore the regulation of interface on MoS_(2)supported Pt nanocrystals which were prepared by reducing ultrasonic dispersed potassium chloroplatinate.The Pt-MoS_(2)heterostructure interface was systematically studied by aberration corrected transmission electron microscopy.Three types of Pt-MoS_(2)interfaces with distinct atomic configurations were identified.The strain within the Pt nanocrystals is sensitive to the atomic configuration of the supporting MoS_(2),which regulates the size of the Pt nanocrystals.These results provide insights on tuning of nanocrystal strain,paving the way for precise control of 2D semiconductor heterostructures.