Molybdenum (Mo) thin films are widely used as back contact layers for thin film solar cells. In this work, Mo layers were deposited by radio-frequency (RF) magnetron sputtering at elevated substrate ...temperature, and their electrical and adhesion properties were investigated with regard to sputtering power and sputtering gas pressure. The crystal structure and morphology of the films were studied using X-ray diffractometry, scanning electron microscopy and atomic force microscopy. It was found that lower pressure and higher power of RF sputtering resulted in lower resistivity of Mo films due to increased kinetic energy of sputtered particles, which improved the crystallinity and compactness of the films. However, bad adhesion was observed for those films with desirable resistivity, exhibiting compressive stress. Through continuous deposition under higher and then lower sputtering gas pressures, a bi-layer Mo film was obtained with desired microstructure and surface morphology, possessing of a low resistivity of 11.1 mu Omega cm and excellent adhesion property.
► We prepared Ni–CdS thin films by a facile spray pyrolysis using perfume atomizer on glass substrate. ► We studied the effect of Ni/Cd ratio on the structural, morphological, optical and electrical ...properties of Ni-doped CdS thin films. ► CdS thin films doped with 4% Ni showed high transmittance of about 80% in the visible and near infrared regions, and relatively low resistivity of 1.3×105Ωcm.
Un-doped and Ni-doped cadmium sulphide (Ni–CdS) thin films were prepared by spray pyrolysis technique using perfume atomizer, from aqueous solution of hydrated cadmium chloride (CdCl2⋅H2O) and thiourea (CS(NH2)2 as sources of cadmium and sulphur ions respectively. We used hexahydrated nickel chloride (NiCl2⋅6H2O) as the dopant. The films were deposited on heated amorphous glass substrates at 400°C. The effect of the Ni/Cd ratio on the structural, morphological, optical and electrical properties of these films was investigated. X-ray diffraction (XRD) studies revealed that all the deposited films (un-doped and Ni-doped CdS) were polycrystalline with hexagonal structure and exhibited 101 preferential orientation. The scanning electron microscopy (SEM) images showed a dense surface structure composed of crystallites whose average size decreases when the Ni/Cd ratio increases. The optical study showed that all the films were highly transparent. The transmittance in the visible region varies between 70% and 85%, depending on the dopant concentration. The film obtained with the Ni/Cd ratio equal to 4at.% Ni showed minimum resistivity of 1.3×105Ωcm at room temperature.
CZTSSe thin films were deposited by selenization of single step electrodeposited CZTS thin films. The properties of CZTSSe thin films were significantly improved by optimizing Se vaporization ...temperature.
•CZTS precursor thin films are prepared by single step electrodeposition method.•The properties of CZTSSe thin films depend on Se vaporization temperature.•The compact CZTSSe thin films can be used as absorber in thin film solar cells.
Cu2ZnSn(SxSe1−x)4 (CZTSSe) thin films are prepared by selenizing a single-step electrodeposited Cu–Zn–Sn–S precursor. The effect of the selenium (Se) vaporization temperature on the properties of CZTSSe thin films is systematically investigated. The position of the (112) peak is systematically shifted to lower 2θ values when the Se vaporization temperature increases. The Raman spectra of CZTSSe films show bimodal behavior. The microstructure and film thickness significantly improve with increasing Se vaporization temperature. The increased Se incorporation in CZTSSe films with the increase of the Se vaporization temperature is demonstrated using a compositional analysis. The band gap energy of CZTSSe thin films is tuned in the range of 1.40–1.08eV by varying the Se vaporization temperature.
•Failure of GeSn nanowire growth was found when Sn and SnO2 thin films were used.•Sparse catalyst and inhibition of catalyst wetting are two key factors to ensure the growth of GeSn nanowires.•Ge ...nanocrystals with good quality were grown from ITO thin films when there is no interfacial SiOx layer.•Controlling of the morphology of GeSn nanowires is realized by changing the annealing environments.
The formation of Sn catalyst nanoparticles (NPs) for the growth of GeSn nanowires (NWs) requires the identification of suitable Sn-containing precursors. In this work, various Sn-containing precursors such as Sn, SnO2 and indium tin oxide (ITO) thin films as well as SnO2 nanoparticles have been investigated. Sn and SnO2 thin films did not produce NWs. This reveals that the catalyst density, as well as their wetting on the amorphous layer, play vital roles on the growth of GeSn NWs. Conversely, Ge nanocrystals (NCs) were successfully grown from ITO thin films deposited on c-Si substrates. A good crystallinity was obtained when there is no interfacial SiOx layer on the crystalline Si substrate. Finally, using SnO2 NPs allowed us to grow GeSn NWs. Their morphology is strongly impacted by the annealing environment: hydrogen atmosphere with different pressures or hydrogen plasma, the later providing the best results. The nanostructure and composition of GeSn NWs were investigated in detail. These results could pave the way to grow in-plane Ge nanostructures within several types of Sn-containing materials.
Since the report of the first diketopyrrolopyrrole (DPP)‐based polymer semiconductor, such polymers have received considerable attention as a promising candidate for high‐performance polymer ...semiconductors in organic thin‐film transistors (OTFTs). This Progress Report summarizes the advances in the molecular design of high‐mobility DPP‐based polymers reported in the last few years, especially focusing on the molecular design of these polymers in respect of tuning the backbone and side chains, and discussing the influences of structural modification of the backbone and side chains on the properties and device performance of corresponding DPP‐based polymers. This provides insights for the development of new and high‐mobility polymer semiconductors.
The advances in molecular design of high‐mobility DPP‐based polymers reported in the past few years are summarized, focusing on the strategy for synthesis of these polymers with respect to tuning the backbone and side chains. The relationships between the chemical structure, molecular packing, transistor characteristics, for example, are discussed.
Writing and Deleting Single Magnetic Skyrmions Romming, Niklas; Hanneken, Christian; Menzel, Matthias ...
Science (American Association for the Advancement of Science),
08/2013, Letnik:
341, Številka:
6146
Journal Article
Recenzirano
Odprti dostop
Topologically nontrivial spin textures have recently been investigated for spintronic applications. Here, we report on an ultrathin magnetic film in which individual skyrmions can be written and ...deleted in a controlled fashion with local spin-polarized currents from a scanning tunneling microscope. An external magnetic field is used to tune the energy landscape, and the temperature is adjusted to prevent thermally activated switching between topologically distinct states. Switching rate and direction can then be controlled by the parameters used for current injection. The creation and annihilation of individual magnetic skyrmions demonstrates the potential for topological charge in future information-storage concepts.
van der Waals heterostructures constitute a new class of artificial materials formed by stacking atomically thin planar crystals. We demonstrated band structure engineering in a van der Waals ...heterostructure composed of a monolayer graphene flake coupled to a rotationally aligned hexagonal boron nitride substrate. The spatially varying interlayer atomic registry results in both a local breaking of the carbon sublattice symmetry and a long-range moiré superlattice potential in the graphene. In our samples, this interplay between short-and long-wavelength effects resulted in a band structure described by isolated superlattice minibands and an unexpectedly large band gap at charge neutrality. This picture is confirmed by our observation of fractional quantum Hall states at ±5/3 filling and features associated with the Hofstadter butterfly at ultrahigh magnetic fields.
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