Van der Waals epitaxy of continuous thin films of 2D materials using atomic layer deposition in low temperature and low vacuum conditions

Van der Waals epitaxy holds great promise in producing high-quality films of 2D materials. However, scalable van der Waals epitaxy processes operating at low temperatures and low vacuum conditions are lacking. Herein, atomic layer deposition is used for van der Waals epitaxy of continuous multilayer films of 2D materials HfS2, MoS2, SnS2, and ZrS2 on muscovite mica and PbI2 on sapphire at temperatures between 75 degrees C and 400 degrees C. For the metal sulfides on mica, the main epitaxial relation is MS2 mica. Some domains rotated by 30 degrees are also observed corresponding to the MS2 mica alignment. In both cases, the presence of domains rotated by 60 degrees (mirror twins) is also expected. For PbI2 on sapphire, the epitaxial relation is PbI2 Al2O3 with no evidence of 30 degrees domains. For all of the studied systems there is relatively large in-plane mosaicity and in the PbI2/Al2O3 system some non-epitaxial domains are also observed. The study presents first steps of an approach towards a scalable and semiconductor industry compatible van der Waals epitaxy method.Peer reviewe

Nonlinear shot noise in mesoscopic diffusive normal-superconducting systems

We study differential shot noise in mesoscopic diffusive normal-superconducting (NS) heterostructures at finite voltages where nonlinear effects due to the superconducting proximity effect arise. A numerical scattering-matrix approach is adopted. Through an NS contact, we observe that the shot noise shows a reentrant dependence on voltage due to the superconducting proximity effect but the differential Fano factor stays approximately constant. Furthermore, we consider differential shot noise in the structures where an insulating barrier is formed between normal and superconducting regions and calculate the differential Fano factor as a function of barrier height.Comment: 4 pages, 6 figure

Silicon oxide-niobium oxide mixture films and nanolaminates grown by atomic layer deposition from niobium pentaethoxide and hexakis(ethylamino) disilane

Amorphous SiO2-Nb2O5 nanolaminates and mixture films were grown by atomic layer deposition. The films were grown at 300 degrees C from Nb(OC2H5)(5), Si-2(NHC2H5)(6), and O-3 to thicknesses ranging from 13 to 130 nm. The niobium to silicon atomic ratio was varied in the range of 0.11-7.20. After optimizing the composition, resistive switching properties could be observed in the form of characteristic current-voltage behavior. Switching parameters in the conventional regime were well defined only in a SiO2:Nb2O5 mixture at certain, optimized, composition with Nb:Si atomic ratio of 0.13, whereas low-reading voltage measurements allowed recording memory effects in a wider composition range.Peer reviewe

IST-2000-30148 I-METRA: D4 Performance evaluation

This document considers the performance of multiantenna transmit/receive techniques in high-speed downlink and uplink packet access. The evaluation is done using both link and system level simulations by taking into account link adaptation and packet retransmissions. The document is based on the initial studies carried out in deliverables D3.1 and D3.2.Preprin

Toward epitaxial ternary oxide multilayer device stacks by atomic layer deposition

The authors demonstrate multilayer epitaxial films by atomic layer deposition and postdeposition annealing. Their example features two ABO(3) type perovskite oxide films with different materials properties-a conductor (LaNiO3) and an insulator (SrTiO3)-that can be integrated epitaxially once the geometric interaction between the two oxides' lattices is understood. Once preliminary epitaxial materials had been developed, the pilot multilayer device fabricated was an epitaxial metal-insulator-metal structure with layers of similar to 5 nm thickness. This work shows the potential for advanced device types based on epitaxial atomic layer deposited films, assuming that care is taken in the selection of processes and starting substrate. Published by the AVS.Peer reviewe

Studies on solid state reactions of atomic layer deposited thin films of lithium carbonate with hafnia and zirconia

In this paper, results on the solid state reactions of atomic layer deposited Li2CO3 with HfO2 and ZrO2 are reported. An Li2CO3 film was deposited on top of hafnia and zirconia, and the stacks were annealed at various temperatures in air to remove the carbonate and facilitate lithium diffusion into the oxides. It was found that Li+ ions are mobile in hafnia and zirconia at high temperatures, diffusing to the film-substrate interface and forming silicates with the Si substrate during heating. Based on grazing incidence x-ray diffraction experiments, no changes in the oxide phases take place during this process. Field emission scanning electron microscopy images reveal that some surface defects are formed on the transition metal oxide surfaces during lithium diffusion. The authors also show that lithium can diffuse through hafnia and react with a potential lithiumion battery electrode material TiO2 residing below the HfO2 layer, forming Li2TiO3. Published by the AVS.Peer reviewe

Atomic layer deposition and properties of mixed Ta2O5 and ZrO2 films

Thin solid films consisting of ZrO2 and Ta2O5 were grown by atomic layer deposition at 300 degrees C. Ta2O5 films doped with ZrO2, TaZr2.75O8 ternary phase, or ZrO2 doped with Ta2O5 were grown to thickness and composition depending on the number and ratio of alternating ZrO2 and Ta2O5 deposition cycles. All the films grown exhibited resistive switching characteristics between TiN and Pt electrodes, expressed by repetitive current-voltage loops. The most reliable windows between high and low resistive states were observed in Ta2O5 films mixed with relatively low amounts of ZrO2, providing Zr to Ta cation ratio of 0.2. (C) 2017 Author(s).Peer reviewe

Atomic Layer Deposition and Performance of ZrO2-Al2O3 Thin Films

Thin mixed and nanolaminate films of ZrO2 and Al2O3 were grown by atomic layer deposition from the corresponding metal chlorides and water. The films were grown at 350 degrees C in order to ensure ZrO2 crystallization in the as-deposited state. The relative thicknesses of layers in the structure of the nanolaminates were controlled in order to maximize the content of metastable polymorphs of ZrO2 that have higher permittivity than that of the stable monoclinic ZrO2 . The multilayer films demonstrated interfacial charge polarization and saturative magnetization in external fields. The conductivity of the films could be switched between high and low resistance states by applying voltages of alternating polarity. (C) 2018 The Electrochemical Society.Peer reviewe

As2S3 thin films deposited by atomic layer deposition

As2S3 thin films were deposited on glass and silicon (100) substrates by atomic layer deposition from tris(dimethylamino) arsine [(CH3)(2)N)(3)As] and H2S. Amorphous films were deposited at an exceptionally low temperature of 50 degrees C. No film growth was observed at higher temperatures. The films were amorphous and contained H and C as the main impurities. The refractive index was 2.3 at 1.0 mu m. The films were sensitive to air humidity, but their stability was significantly improved by a protective Al2O3 layer. (C) 2016 American Vacuum Society.Peer reviewe

Magnetic properties and resistive switching in mixture films and nanolaminates consisting of iron and silicon oxides grown by atomic layer deposition

SiO2-Fe2O3 mixture films and nanolaminates were grown by atomic layer deposition from iron trichloride, hexakis(ethylamino)disilane, and ozone at 300 degrees C. Orthorhombic -Fe2O3 was identified in Fe2O3 reference films and in Fe2O3 layers grown to certain thicknesses between amorphous SiO2 layers. SiO2-Fe2O3 films could be magnetized in external fields, exhibiting saturation and hysteresis in nonlinear magnetization-field curves. Electrical resistive switching, markedly dependent on the ratio of the component oxides, was also observed in films with proper composition. For relatively conductive films, application of small signal measurements allowed one to record memory maps with notable squareness and defined distinction between high and low conductance states.Peer reviewe