Influence of the thickness of Si and Ge films deposited on Si$_3$N$_4$/SiO$_2$/Si substrates on their structure and diffusion of hydrogen atoms from Si$_3$N$_4$ layers
Larisa V. Arapkina, Kirill V. Chizh, Dmitry B. Stavrovskii, Alexey A. Klimenko, Alexander A. Dudin, Vladimir P. Dubkov, Mikhail S. Storozhevykh, Vladimir A. Yuryev
The results of RHEED, FTIR and Raman spectroscopy study of silicon and germanium films with the thickness up to 200 nm grown from molecular beams on dielectric Si$_3$N$_4$/SiO$_2$/Si(001) substrates are presented. Noticeable changes of the intensity of the N$-$H and Si$-$N absorption bands have been observed in the IR absorbance spectra as a result of the deposition of the silicon and germanium films. The thicker was the deposited film, the more considerable were the decrease of N$-$H absorption band intensity and the increase in that of the Si$-$N band. This tendency has been observed during the growth of both amorphous and polycrystalline Si or Ge films. The reduction of IR absorption at the band assigned to the N$-$H bond vibration is explained by breaking of these bonds followed by the diffusion of the hydrogen atoms from the Si$_3$N$_4$ layer into the growing film of silicon or germanium. The effect of the deposited film thickness on the diffusion of hydrogen is discussed within a model of the diffusion of hydrogen atoms controlled by the difference in chemical potentials of hydrogen atoms in the dielectric Si$_3$N$_4$ layer and the growing silicon or germanium film. Hydrogen atoms escape from the Si$_3$N$_4$ layer only during the deposition of a Si or Ge film when its thickness gradually grows. The interruption of the film growth stops the migration of hydrogen atoms into the film because of the decline in the chemical potential difference.
We use first-principles simulations to investigate the topological properties of Bi$_2$Se$_3$ thin films deposited on amorphous SiO2, Bi$_2$Se$_3$/a-SiO$_2$, which is a promising substrate for topological insulator (TI) based device applications. The Bi$_2$Se$_3$ films are bonded to a-SiO$_2$ mediated by van der Waals interactions. Upon interaction with the substrate, the Bi$_2$Se$_3$ topological surface and interface states remain present, however the degeneracy between the Dirac-like cones is broken. The energy separation between the two Dirac-like cones increases with the number of Bi$_2$Se…
The electronic structure of an atomic-layer-deposited MoS2 monolayer on SiO2 was investigated using X-ray absorption spectroscopy (XAS) and synchrotron X-ray photoelectron spectroscopy (XPS). The angle-dependent evolution of the XAS spectra and the photon-energy-dependent evolution of the XPS spectra were analyzed in detail using an ab-initio electronic structure simulation. Although similar to the theoretical spectra of an ideal free-standing MoS2 ML, the experimental spectra exhibit features that are distinct from those of an ideal ML, which can be interpreted as a consequence of S-O van der…
Amorphous silica (a-SiO2) exhibits unique thermo-mechanical behaviors that set it apart from other glasses. However, there is still limited understanding of how this mechanical behavior is related to the atomic structure and to the preparation conditions of a-SiO2. Here, we used electron beam (e-beam) physical vapor deposition (PVD) to prepare a series of a-SiO2 films grown at different substrate temperatures and then combined molecular simulations with Positronium Annihilation Lifetime Spectroscopy and nanoindentation experiments to establish relations among processing, structure, and mechani…
In this paper, SiO2 layers deposited on 4H-SiC and subjected to different post deposition annealing (PDA) in NO and N2O were studied to identify the key factors influencing the channel mobility and threshold voltage stability in 4H-SiC MOSFETs. In particular, PDA in NO gave a higher channel mobility (55 cm2V-1s-1) than PDA in N2O (20 cm2V-1s-1), and the subthreshold behavior of the devices confirmed a lower total amount of interface states for the NO case. This latter could be also deduced from the behavior of the capacitance-voltage characteristics of 4H-SiC MOSFETs measured in gate controlle…
In the paper, the processes occurring during low-temperature growth of non-hydrogenated amorphous Si and polycrystalline Si films on multilayer Si$_3$N$_4$/SiO$_2$/c-Si substrates from molecular beams under conditions of ultrahigh vacuum are studied in detail. Diffusion of hydrogen atoms from a dielectric layer into the growing film is shown to accompany the growth of a silicon film on a Si$_3$N$_4$ layer deposited by CVD or on a SiO$_2$ layer obtained by thermal oxidation of a silicon wafer. The process of hydrogen migration from the dielectric substrates into the silicon film is studied usin…
Inspired by nature, we investigate the short-range order effect on the physical properties of amorphous materials. Amorphous Al2O3 thin films exhibit a higher proportion of their 4-coordinated Al sites close to the surface, causing variations in the average short-range order of the film. Below some thickness, the density of these films changes with size. In this work, we address the short-range order effect, through the thickness, on the electronic and optical properties of atomic layer deposited (ALD) Al2O3 thin films. Both the refractive index and the permittivity were found to vary with siz…
The development of advanced spintronics devices hinges on the efficient generation and utilization of pure spin current. In materials with large spin-orbit coupling, the spin Hall effect may convert charge current to pure spin current and a large conversion efficiency, which is quantified by spin Hall angle (SHA), is desirable for the realization of miniaturized and energy efficient spintronic devices. Here, we report a giant SHA in beta-tungsten (\b{eta}-W) thin films in Sub/W(t)/Co20Fe60B20(3 nm)/SiO2(2 nm) heterostructures with variable W thickness. We employed an all-optical time-resolved …
The study of hexagonal silicon polytypes attracts special attention due to their unique physical properties compared to the traditional cubic phase of Si. Thus, for some hexagonal phases, a significant improvement in the emission properties has been demonstrated. In this work, the luminescent properties of SiO2/Si structures irradiated with Kr+ ions at different doses and annealed at 800 °C have been systematically investigated. For such structures, a photoluminescence line at ~ 1240 nm is observed and associated with the formation of hexagonal 9R-Si phase inclusions. It is found that the vari…
Topological insulators are immensely investigated for their surface states related properties as these materials can be used for various spintronics, quantum computing, and optoelectronics applications. In this perspective, different thicknesses of bismuth selenide thin films are deposited on the 250 nm SiO2 substrate with the help of thermal deposition. The motive of this study is to investigate the surface and bulk-related behaviour with different thicknesses. The deposited films are characterized through GI-XRD (grazing incidence X-ray diffractometer) and Raman spectroscopy, which ensure th…
Titanium (Ti), due to its excellent properties, is widely exploited in thin film technology that usually leads to the production of α-phase (hcp) Ti films. In this work, we investigate the phase evolution of Ti films deposited by varying type and energy of the film-forming species. To investigate different plasma species environments, films with different thicknesses are grown by using conventional Direct Current Magnetron Sputtering (DCMS) and High Power Impulse Magnetron Sputtering (HiPIMS). Furthermore, HiPIMS depositions with different substrate bias voltage US (0 V, -300 V and -500 V) are…
Boron carbide thin films of different thicknesses deposited by ion beam sputtering were studied. The deposited films were characterized by grazing incidence hard x-ray reflectivity (GIXR), resonant soft x-ray reflectivity (RSXR), x-ray photo electron spectroscopy (XPS), resonant Rutherford backscattering spectrometry (RRBS), and time of flight secondary ion mass spectrometry (TOF-SIMS). An in-depth profile of the chemical elements constitute the films is reconstructed based on analysis of reflectivity curves measured in the vicinity of B K-edge. The composition of films is closely dependent on…
Large-area growth of continuous transition metal dichalcogenides (TMDCs) layers is a prerequisite to transfer their exceptional electronic and optical properties into practical devices. It still represents an open issue nowadays. Electric and magnetic doping of TMDC layers to develop basic devices such as p-n junctions or diluted magnetic semiconductors for spintronic applications are also an important field of investigation. Here, we have developed two different techniques to grow MoSe$_2$ mono- and multi-layers on SiO$_2$/Si substrates over large areas. First, we co-deposited Mo and Se atoms…
Thickness dependent rare earth segregation in magnetron deposited NdCo$_{4.6}$ thin films studied by Xray reflectivity and Hard Xray photoemission
Universidad de Oviedo（奥维耶多大学）；CINN (CSIC-Universidad de Oviedo)（凝聚态物质综合研究所（西班牙国家研究委员会-奥维耶多大学））；SpLine Spanish CRG Beamline at the ESRF（欧洲同步辐射装置 SpLine 西班牙 CRG 光束线）；Instituto de Ciencia de Materiales de Madrid-ICMM/CSIC（马德里物质科学研究所）
Nearly two-orders of magnitude increase in room-temperature band-to-band (1.067 eV) infrared emission from crystalline silicon, coated with erbium-doped sol-gel films, have been achieved. Phonon-assisted band-to-band emission from coated and annealed p-Si is strongest for the sample annealed at 700$^{\circ}$C. In this paper, evidence of the origin of the emission band from the band edge recombination activities is established. Enhancement of radiative recombination of free carriers is reasoned by stresses at the interface due to the annealed sol-gel deposited silica. Comparative studies with o…
High mobility and high on/off ratio field-effect transistors based on chemical vapor deposited single-crystal MoS2 grains
我们报告了场效应晶体管（FET）与单晶二硫化钼（MoS 2）的化学气相沉积（CVD）合成的通道。对于双层MoS 2 FET，迁移率为~17 cm ~ 2 V ~（-1）s ~（-1），开/关电流比为~108，这比基于CVD多晶MoS 2膜的FET高得多。通过避免由转移过程引入的晶界和污染的有害影响，直接沉积在SiO2上的CVD MoS 2原子层的质量与最佳剥离的MoS 2薄片相当。结果表明，CVD法是制备高质量MoS_2原子层的一种可行方法。
Two-dimensional (2D) WS2 films were deposited on SiO2 wafers, and the related interfacial properties were investigated by high-resolution x-ray photoelectron spectroscopy (XPS) and first-principles calculations. Using the direct (indirect) method, the valence band offset (VBO) at monolayer WS2/SiO2 interface was found to be 3.97 eV (3.86 eV), and the conduction band offset (CBO) was 2.70 eV (2.81 eV). Furthermore, the VBO (CBO) at bulk WS2/SiO2 interface is found to be about 0.48 eV (0.33 eV) larger due to the interlayer orbital coupling and splitting of valence and conduction band edges. Ther…
We report the influence of the AlN interlayer thickness (0-15 nm) on the photovoltaic properties of Al0.37In0.63N on Si heterojunction solar cells deposited by radio frequency sputtering. The poor junction band alignment and the presence of a 2-3 nm thick amorphous layer at the interface mitigates the response in devices fabricated by direct deposition of n-AlInN on p-Si(111). Adding a 4-nm-thick AlN buffer layer improves the AlInN crystalline quality and the interface alignment leading to devices with a conversion efficiency of 1.5% under 1-sun AM1.5G illumination. For thicker buffers the per…
Growth mode, magnetic and magneto-optical properties of pulsed-laser-deposited Au/Co/Au(111) trilayers
研究了超高真空下脉冲激光沉积（PLD）外延Au/Co/Au（111）多层膜的生长模式、磁性和磁光特性。用单晶Mo（110）双层缓冲的蓝宝石晶片用作衬底。由于PLD诱导的界面混合在较低的Co/Au（111）界面，逐层生长模式得到促进。令人惊讶的是，尽管这种混合，铁磁行为被发现在室温下的覆盖物开始在1个原子层（AL）。该膜显示垂直磁化与各向异性常数减少了50%相比，TD生长或电沉积的膜，并具有一个以上的数量级低（$\lesssim$ 5 mT）的磁化率。在低Co厚度范围内的磁光（MO）响应主要由Au/Co界面的贡献。对于开始于3 AL Co的厚度，MO响应具有与Co厚度的线性依赖性，指示连续膜状MO行为。
We have investigated the magnetodynamic properties of $\text{La}_{0.7}\text{Sr}_{0.3}\text{MnO}_3$ (LSMO) films of thickness 10, 15 and 30 nm grown on (111)-oriented SrTi$\text{O}_3$ (STO) substrates by pulsed laser deposition. Ferromagnetic resonance (FMR) experiments were performed in the temperature range 100--300 K, and the magnetodynamic damping parameter $α$ was extracted as a function of both film thickness and temperature. We found that the damping is lowest for the intermediate film thickness of 15 nm with $α\approx 2 \cdot 10^{-3}$, where $α$ is relatively constant as a function of t…
Thin films of phase pure pyrochlore Gd2Ti2O7 have been synthesized by RF magnetron sputtering. The films were prepared from oxide targets in 50%O2/Ar atmosphere and deposited on 111 YSZ substrates at a temperature of 800C. The pyrochlore structure was confirmed via grazing angle x-ray diffraction and selected area electron diffraction (SAED). TEM analysis also showed that the films were dense and of uniform thickness with surface roughness of approximately 8nm. The total conductivity measured with AC impedance spectroscopy was found to be independent of thickness and comparable in magnitude to…
We have grown Au/Ag modulated nanostructured thin films by pulsed laser deposition using metallic targets. The growths performed at room temperature involved deposition of alternate layers of the two metals with larger thickness of Au and much lower thickness of Ag (two cases) on crystalline silicon (100) and quartz substrates. However, the characterization revealed that nanostructured configuration is realized in the film. We characterized the films by x-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM) with energy dispersive analysis of x-rays (EDAX), magnetization (…
Indium selenide (InSe), as a novel van der Waals layered semiconductor, has attracted a large research interest thanks to its excellent optical and electrical properties in the ultra-thin limit. Here, we discuss four different optical methods to quantitatively identify the thickness of thin InSe flakes on various substrates, such as SiO2/Si or transparent polymeric substrates. In the case of thin InSe deposited on a transparent substrate, the transmittance of the flake in the blue region of the visible spectrum can be used to estimate the thickness. For InSe supported by SiO2/Si, the thickness…
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 a…
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…
Ferromagnetic resonance (FMR) technique has been used to study the magnetization relaxation processes and magnetic anisotropy in two different series of the Co2FeSi (CFS) Heusler alloy thin films, deposited on the Si(111) substrate by UHV sputtering. While the CFS films of fixed (50 nm) thickness, deposited at different substrate temperatures (TS) ranging from room temperature (RT) to 600^C, constitute the series-I, the CFS films with thickness t varying from 12 nm to 100 nm and deposited at 550^C make up the series-II. In series-I, the CFS films deposited at TS = RT and 200^C are completely a…
Electric control of magnetic properties is an important challenge for modern magnetism and spintronic development. In particular, an ability to write magnetic state electrically would be highly beneficial. Among other methods, the use of electric field induced deformation of piezoelectric elements is a promising low-energy approach for magnetization control. We investigate the system of piezoelectric substrate Pb[Zr$_x$Ti$_{1-x}$]O$_3$ with CoFe overlayers, extending the known reversible bistable electro-magnetic coupling to surface and multistate operations, adding the initial state reset pos…
Effect of Top Al$_2$O$_3$ Interlayer Thickness on Memory Window and Reliability of FeFETs With TiN/Al$_2$O$_3$/Hf$_{0.5}$Zr$_{0.5}$O$_2$/SiO$_x$/Si (MIFIS) Gate Structure
We have implemented three different optical methods to quantitatively assess the thickness of thin GaSe flakes transferred on both transparent substrates, like Gel-Film, or SiO2/Si substrates. We show how their apparent color can be an efficient way to make a quick rough estimation of the thickness of the flakes. This method is more effective for SiO2/Si substrates as the thickness dependent color change is more pronounced on these substrates than on transparent substrates. On the other hand, for transparent substrates, the transmittance of the flakes in the blue region of the visible spectrum…
3D lattice Monte Carlo modeling of morphology formation of Si/SiOx nanocomposites during phase separation of nonstoichiometric Si oxide films
Educational Scientific Institute of High Technologies, Taras Shevchenko National University of Kyiv（基辅塔拉斯舍甫琴科国立大学高等技术教育科学研究所）；V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine（乌克兰国家科学院瓦西里拉什卡廖夫半导体物理研究所）；National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”（乌克兰国立技术大学“伊戈尔·西科尔斯基基辅理工学院”）
Zinc Oxide (ZnO) semiconductor is ideal candidates for ultra-violet (UV) photodetector due to its promising optoelectronic properties. Photodetectors based on ZnO nanostructures show very high photoconductivity under UV light, but they are plagued by slow photo-response time as slow as several tens of hours, even more. Most of the studies claimed that atmospheric adsorbates such as water and oxygen create charge traps states on the surface and remarkably increase both the photoconductivity and response time, but there are also limited studies that claiming the defect induced states acting as h…
High Mobility Ambipolar MoS2 Field-Effect Transistors: Substrate and Dielectric Effects
我们在二氧化硅和聚甲基丙烯酸甲酯（PMMA）衬底上制作了二硫化钼场效应晶体管，并在四探针配置中测量了载流子迁移率。对于SiO2上的多层MoS 2，迁移率为30-60 cm 2/Vs，与厚度（15-90 nm）相对无关，并且大多数器件表现出单极n型行为。相比之下，PMMA上的多层MoS 2显示出随厚度增加的迁移率，在厚度约50 nm处高达470 cm 2/Vs（电子）和480 cm 2/Vs（空穴）。迁移率对厚度的依赖性指向在增加迁移率中的块状MoS 2的长程介电效应。
Barrium fluoride (BaF2) thin films were prepared by electron beam evaporation technique at room temperature, on glass, Silicon and Aluminum substrates having thickness of 20 nm each. Its structural property and surface morphology were studied using glancing angle X-ray diffraction (GAXRD) and atomic force microscopy (AFM) respectively. It was found that grain size, average surface roughness and interface width changes with different substrates. Higuchi algorithm is applied for the fractal measure on AFM images.It was observed found that the fractal dimension varied from substrate to substrate.
We performed Scanning Thermal Microscopy measurements on single layers of chemical-vapor-deposited -CVD- graphene supported by different substrates, namely SiO2, Al2O3 and PET using a double-scan technique to remove the contribution to the heat flux through the air and the cantilever. Then, by adopting a simple lumped-elements model, we developed a new method that allows determining, through a multi-step numerical analysis, the equivalent thermal properties of thermally conductive coatings of nanometric thickness. In this specific case we found that our CVD graphene is thermally equivalent, fo…
