Two-step Evaporation Method Research Articles

Full-color fiber light-emitting diodes based on perovskite quantum wires.

Fiber light-emitting diodes (Fi-LEDs), which can be used for wearable lighting and display devices, are one of the key components for fiber/textile electronics. However, there exist a number of impediments to overcome on device fabrication with fiber-like substrates, as well as on device encapsulations. Here, we uniformly grew all-inorganic perovskite quantum wire arrays by filling high-density alumina nanopores on the surface of Al fibers with a dip-coating process. With a two-step evaporation method to coat a surrounding transporting layer and semitransparent electrode, we successfully fabricated full-color Fi-LEDs with emission peaks at 625 nanometers (red), 512 nanometers (green), and 490 nanometers (sky-blue), respectively. Intriguingly, additional polydimethylsiloxane packaging helps instill the mechanical bendability, stretchability, and waterproof feature of Fi-LEDs. The plasticity of Al fiber also allows the one-dimensional architecture Fi-LED to be shaped and constructed for two-dimensional or even three-dimensional architectures, opening up a new vista for advanced lighting with unconventional formfactors.

Temperature-responsive binary superlattices prepared by the selective solvent evaporation of O/W microemulsion composed of gold nanoparticles and surfactants.

Binary nanoparticle superlattices (BNSLs) are one of the important classes of nanomaterial architectures for a wide range of potential applications because they can provide synergistically enhanced properties depending on the morphology and spatial arrangement of nanoparticles (NPs). However, although many studies have been conducted on the fabrication of BNSLs, there are still several challenges in achieving BNSLs with a three-dimensional lattice due to their complicated synthesis, hindering their practical applications. Herein, we report the fabrication of temperature-sensitive BNSLs in complexes of gold nanoparticles (AuNPs), Brij 58 surfactant, and water via a two-step evaporation method. The surfactant was utilized for two different purposes, i.e., surface modification of the AuNPs to control their interfacial energy and as a template material for the formation of the superlattice. Depending on the size and concentration of the AuNPs, the mixture of AuNPs and surfactant self-assembled into three types of BNSLs, including CaF2, AlB2, and NaZn13, which were sensitive to temperature. This study is the first demonstration of the temperature- and particle size-dependent control of BNSLs in the bulk state without the covalent functionalization of NPs via a simple two-step solvent evaporation method.

Fabrication of BaSi2 homojunction diodes on Nb-doped TiO2 coated glass substrates by aluminum-induced crystallization and two-step evaporation method

BaSi2 homojunction diodes on Nb-doped TiO2 (TiO2:Nb) coated glass substrates were fabricated using aluminum-induced crystallization (AIC) and a two-step evaporation method. From Raman scattering spectra, the growth of BaSi2 on TiO2:Nb was confirmed when the thickness of poly-Si grown by AIC (AIC-Si) was more than 150 nm. The partial formation of BaSi2 diodes was confirmed from the samples prepared at temperature during AIC T AIC = 475 °C–525 °C. The long-wavelength edge of photoresponsivity of the diodes was located around 950 nm, which corresponds to the bandgap of BaSi2 of 1.3 eV, suggesting that this photocurrent is derived from BaSi2 thin films. At T AIC = 500 °C, the maximum value of photoresponsivity was obtained. Since the largest grains in AIC-Si were also obtained at T AIC = 500 °C, these results suggest that larger grain of AIC-Si leads to the improvement of the quality of BaSi2 thin films themselves and the performance of BaSi2 diodes.

Fabrication of heterojunction crystalline Si solar cells with BaSi2 thin films prepared by a two-step evaporation method

We have fabricated p-type BaSi2 (p-BaSi2)/n-type crystalline Si (n-c-Si) heterojunction solar cells using thermal evaporation. To control the defect around the heterointerface, samples were fabricated by two methods using different current profiles during evaporation. The one-step method was designed to avoid supplying Ba-rich vapor, and the two-step method was designed to intentionally introduce Ba-rich vapor at the first step. Deep-level transient spectroscopy measurements revealed that defect densities in the n-c-Si side were almost the same for both samples. Open-circuit voltage (V oc) was successfully improved from 319 to 463 mV by the two-step method. This may be due to the increase of carrier density in p-BaSi2 prepared using a two-step method. As a result of optimization, the conversion efficiency of 6.23% was achieved by the heterojunction solar cells.

Surface Morphology and Device Performance of CuInS2 Solar Cells Prepared by Single- and Two-Step Evaporation Methods

Absorbers of CuInS2 (CIS) solar cells are fabricated by several processes and a 11.4% efficiency CIS solar cell is reported. However, this value is lower than the theoretically expected value, possibly owing to the roughness of the CIS surface. In this study, we attempted to realize smoother CIS films using a new two-step evaporation method. As a first step, Cu-rich CIS films were deposited at a low substrate temperature of 50 °C and were annealed at 500 °C. As a second step, In and S were sequentially deposited on the annealed films to control the compositional ratio to In-rich. The deposited film showed a smoother surface than the film deposited by the single-step evaporation of Cu, In, and S. The CIS solar cell formed using the two-step evaporation method showed a higher open-circuit voltage. This should be due to the smoother film surface, which reduced the p–n junction area of the device.

Controllable Fabrication of High-Quality 6-Fold Symmetry-Branched CdS Nanostructures with ZnS Nanowires as Templates

Absolute 6-fold symmetrically branched CdS nanostructures were heteroepitaxially grown with a simple two-step evaporation method. The ZnS nanowires were synthesized in first step and were then used as templates for the following growth of 6-fold symmetrical CdS nanobelts or nanowire at varied temperature in the second step. The orientation relationship between ZnS nanowires and CdS nanobelts was investigated to confirm the effect of crystalline substrates on the epitaxial (1D directional) growth process of branch nanostructures. The photoluminescence spectra of as-synthesized nanostructures displayed a dominant and sharp band edge emission band, only accompanied with a weak and broad trap-state emission band under high excitation at room temperature. The present approach of epitaxial growth of symmetrical nanostructures from presynthesized template nanostructures may supply new opportunities for high-quality complex nanostructure growth, which may find new applications in the researches and devices of such nanostructures.

Silver-based compound metal island films for write-once optical data-storage media

Silver-based compound metal island (CMI) films prepared by use of a two-step evaporation method at the low substrate temperature of 20-30 degrees C have been experimentally investigated for write-once (WO) optical data-storage media. We found that most silver-based CMI films can be used as WO optical data-storage media provided that the island structure is formed in the films. Silver-gold CMI films are particularly useful as more-durable WO media for the 800-nm wavelength as compared with conventional silver island films. Aluminum-silver CMI films are potential WO media for a shorter-wavelength region, since the resonance wavelength exists near 500 nm. The spectral characteristics of the CMI films can be controlled by selection of the mixture ratio and evaporation order of metals. By use of CMI films, various specific WO optical data-storage media could be developed.

Write-once optical data storage media for shorter wavelengths using aluminium-silver compound metal island films

Aluminium (Al)-silver (Ag) compound metal island (CMI) films fabricated by using a two-step evaporation method have been realised for use as write-once (WO) optical data storage media for shorter wavelengths. The Al-Ag CMI films have a high reflectance for blue light as the resonance wavelength exists in the 450–500 nm range. It has been experimentally confirmed that the reflectance of the Al-Ag CMI film is significantly reduced by heating at a temperature of >200°C. This suggests that the Al-Ag CMI films may be useful as WO media for shorter wavelengths with larger storage density.

Silver-gold compound metal island films for durable write-once optical disk memories

Silver-gold compound metal island (CMI) films fabricated by using a two-step evaporation method have been investigated for write-once (WO) optical disk memories. It has been experimentally confirmed that the CMI films are more durable than conventional silver island films reported as potential compact disc-compatible WO memories in previous work. In addition, the reflectance of the CMI film is as high as that of the silver island film at 800 nm and can be significantly reduced by heating the films at 150–200°C. This suggests that the silver-gold CMI films may be useful as write-once optical data storage media.

Characterization of Pb(ZrxTi1−x)O3 films prepared by vacuum evaporation method

Abstract Pb(ZrxTi1−x)O3 (PZT) thin films have been prepared on Pt/MgO substrates by vacuum evaporation technique using PbO and ZrO2/TiO2 pellets as source materials. Good quality PZT can be obtained by employing Two-step evaporation method, where only PbO is evaporated at first before the PZT evaporation. Remanent polarizations of 17–29 μC/cm2 and coercive fields of 45–126 kV/cm are obtained.

Silver-gold compound metal island films prepared by using a two-step evaporation method

A silver-gold compound metal island film prepared by using a two-step evaporation method is demonstrated for the first time. Silver and gold islands have been completely alloyed by heating the film at 300 °C. The resonance wavelength of the compound metal island film exists between those of pure silver and pure gold island films. It is shown that the resonance wavelength can easily be controlled by selection of the mixture ratio of silver and gold.