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In recent years, research attention has increasingly focused on thin-film photovoltaics utilizing Sb2Se3 as an ideal absorber layer. This compound is favored due to its abundance, non-toxic nature, long-term stability, and the potential to employ various cost-effective and scalable vapor deposition (PVD) routes. On the other hand, improving passivation, surface treatment and p-type carrier concentration is essential for developing high-performance and commercially viable Sb2Se3 solar cells. In this study, Cu-doped Sb2Se3 solar devices were fabricated using two distinct PVD techniques, pulsed electron deposition (PED) and radio frequency magnetron sputtering (RFMS). Furthermore, 5%Cu:Sb2Se3 films grown via PED exhibited high open-circuit voltages (VOC) of around 400 mV but very low short-circuit current densities (JSC). Conversely, RFMS-grown Sb2Se3 films resulted in low VOC values of around 300 mV and higher JSC. To enhance the photocurrent, we employed strategies involving a thin NaF layer to introduce controlled local doping at the back interface and a bilayer p-doped region grown sequentially using PED and RFMS. The optimized Sb2Se3 bilayer solar cell achieved a maximum efficiency of 5.25%. [ABSTRACT FROM AUTHOR]

Copper-doped antimony selenide (Cu-doped Sb2Se3) thin films were deposited as absorber layers in photovoltaic solar cells using the low-temperature pulsed electron deposition (LT-PED) technique, starting from Sb2Se3 targets where part of the Sb was replaced with Cu. From a crystalline point of view, the best results were achieved for thin films with about Sb1.75Cu0.25Se3 composition. In order to compare the results with those previously obtained on undoped thin films, Cu-doped Sb2Se3 films were deposited both on Mo- and Fluorine-doped Tin Oxide (FTO) substrates, which have different influences on the film crystallization and grain orientation. From the current-voltage analysis it was determined that the introduction of Cu in the Sb2Se3 absorber enhanced the open circuit voltage (VOC) up to remarkable values higher than 500 mV, while the free carrier density became two orders of magnitude higher than in pure Sb2Se3-based solar cells. [ABSTRACT FROM AUTHOR]

Research was conducted to examine the electrical characteristics of terbium ions in crystalline Si elucidating the role played by defects, thermal annealing and oxygen content in the dissociation and formation of Tb-related complexes. The Si junctions were implanted with 5 MeV Tb ions while some epitaxial Si samples were coimplanted with O. Annealing was performed at temperatures ranging from 800 to 1000 degrees C. Results indicate that O diffusion to Tb ions at approximately 900 degrees C generated the growth and dissolution kinetics of Tb-O complexes.

Nitroaromatic explosives are the most common explosives, and their detection is important to public security, human health, and environmental protection. In particular, the detection of solid explosives through directly revealing the presence of their vapors in air would be desirable for compact and portable devices. In this study, amino-functionalized carbon nanotubes were used to produce resistive sensors to detect nitroaromatic explosives by interaction with their vapors. Devices formed by carbon nanotube networks working at room temperature revealed trinitrotoluene, one of the most common nitroaromatic explosives, and di-nitrotoluene-saturated vapors, with reaction and recovery times of a few and tens of seconds, respectively. This type of resistive device is particularly simple and may be easily combined with low-power electronics for preparing portable devices. [ABSTRACT FROM AUTHOR]

The realization of low resistivity and stable contacts on p-type CdTe is still challenging, especially if high annealing temperatures must be avoided. In this paper, the electrical characteristics of [Sb.sub.2] [Te.sub.3] contacts on p-type CdTe single crystals are studied. It is found that the resistivity of the contacts is low and constant with time.

We report a detailed characterization of Ge NWs directly grown on glass by a MOVPE system, showing how different growth parameters can affect the final outcome and comparing NWs grown on a monocrystalline Ge(111) substrate with NWs grown on amorphous glass. Our experimental results indicate that the choice of the substrate does not affect any of the relevant morphological, crystallographic or electrical properties of Ge NWs. Lengths are in the 20–30 micrometer range with minimal tapering, while growth rates are very similar to to NWs grown on Ge(111); TEM and Raman characterization show a very good crystallinity of measured nanostructures. We have also analyzed the growth process on glass and we were able to reach a conclusion on the specific growth mechanism for Ge NWs on amorphous substrates. Our findings demonstrate that glass is a valid option as cheap substrate for the mass production of these nanostructures. [ABSTRACT FROM AUTHOR]

Infrared photodetectors with In(Ga)As quantum dot (QD) active element functioning on interband and intersubband transitions are currently actively investigated, however, the vertical sensors were mostly reported. In the current study, a multilayer In0.4Ga0.6As/GaAs QD photodetector structure allowing the lateral photocurrent detection at normal incidence has been prepared depositing top contact. In order to have a comparison, a heterostructure with only a stack of In0.4Ga0.6As/GaAs wetting layers (WL) has been grown. In-depth photoelectrical characterization shows an effective broad-band photodetection related to the interband transitions between quantum-confined levels in QDs ranging from 1.03 to 1.38 eV (0.9–1.2 μm) that covers much wider infrared range in comparison to that from WLs (1.27–1.38 eV). Photoluminescence spectroscopy confirms the existence of QD transitions, observed as intense QD emission which peaked at 1.12 eV (∼1 μm) redshifted in comparison to the WL structure. The mechanisms of photoconductivity are modelled and discussed, comparing both the structures. We also show that our QD stack has an order lower contribution from defects compared to similar QD structures investigated before. At the same time, our structures demonstrate appropriate device characteristics at room temperature, such as the wide dynamic range from 10–2 to 103μW cm−2 and a high photoresponsivity up to 20 A W−1 at low excitation intensities over 10–2–10–1μW cm−2, while at higher excitation intensities the responsivity is reduced, exhibiting a strong spectral dependence. Thereby, our results show that the grown multilayer In0.4Ga0.6As/GaAs QD heterostructure is of relevant interest for application in lateral QD photodetectors. [ABSTRACT FROM AUTHOR]

Vertical transport in p-i-n diodes containing InGaP/GaAs multi-quantum-wells (MQW) is investigated using current-voltage measurements under forward bias at different temperatures. At low injection, the experimental data are analyzed through a two diode model, by taking into account the non-complete depletion of the MQW region caused by unintentional p-type doping. The diffusion current results to be dominant at high temperatures, whereas the current due to non-radiative recombination through defects in the space charge region becomes more and more relevant as the temperature is reduced. At temperatures above T = 150 K and at high forward voltages, when the current is limited by the series resistance, the thermionic emission of holes over the InGaP barriers controls the transport through the whole MQW region. At lower temperatures resonant tunneling of holes takes place and a simple picture of the hole quantum levels permits to interpret the main details of the I(V) curves at T = 41 K, by supporting the hypothesis of a uniform electric field in the MQW region up to about 100 kV/cm. [ABSTRACT FROM AUTHOR]

Photoelectrical measurements were taken on a nominally undoped-InGaP/GaAs superlattice, inserted between two p+ and n+ InGaP cladding layers. The sequence of InGaP/GaAs alternated layers forming the superlattice was grown lattice matched on n+-GaAs substrates through low pressure-metal organic vapor phase epitaxy, at growth conditions previously optimized for obtaining sharp interfaces and negligible ordering effects in the cation sublattice of the InGaP layers. A peculiar dependence of both the photocurrent and the photovoltaic signals on the modulation frequency of the exciting light beam was observed and then interpreted according to proper equivalent electrical circuits. The effects induced by an incomplete depletion of the nominally undoped superlattice region are analyzed in detail, and the analogies between photoelectrical investigation and admittance spectroscopy are pointed out. [ABSTRACT FROM AUTHOR]

Examines a hole diffusion length in liquid-encapsulated-Czochralski GaAs monocrystals, using photon and electron bombardment through semitransparent gold and chromium Schottky electrodes. Relationship of the diffusion length investigation carried out by the steady-state surface photovoltage and the scanning electron microscope electron-beam-induced current with the spectral quantum efficiency of Schottky diodes; Methods used to determine the diffusion length L and its equivalent parameter.

The bipolar effect of GaAs substrate and nearby layers on photovoltage of vertical metamorphic InAs/InGaAs in comparison with pseudomorphic (conventional) InAs/GaAs quantum dot (QD) structures were studied. Both metamorphic and pseudomorphic structures were grown by molecular beam epitaxy, using bottom contacts at either the grown n -buffers or the GaAs substrate. The features related to QDs, wetting layers, and buffers have been identified in the photoelectric spectra of both the buffer-contacted structures, whereas the spectra of substrate-contacted samples showed the additional onset attributed to EL2 defect centers. The substrate-contacted samples demonstrated bipolar photovoltage; this was suggested to take place as a result of the competition between components related to QDs and their cladding layers with the substrate-related defects and deepest grown layer. No direct substrate effects were found in the spectra of the buffer-contacted structures. However, a notable negative influence of the n -GaAs buffer layer on the photovoltage and photoconductivity signal was observed in the InAs/InGaAs structure. Analyzing the obtained results and the performed calculations, we have been able to provide insights on the design of metamorphic QD structures, which can be useful for the development of novel efficient photonic devices. [ABSTRACT FROM AUTHOR]

The quest for single-stage deposition of CuInGaSe2 (CIGS) is an open race to replace very effective but capital intensive thin film solar cell manufacturing processes like multiple-stage coevaporation or sputtering combined with high pressure selenisation treatments. In this paper the most recent achievements of Low Temperature Pulsed Electron Deposition (LTPED), a novel single stage deposition process by which CIGS can be deposited at 250 °C, are presented and discussed. We show that selenium loss during the film deposition is not a problem with LTPED as good crystalline films are formed very close to the melting temperature of selenium. The mechanism of formation of good ohmic contacts between CIGS and Mo in the absence of any MoSe2 transition layers is also illustrated, followed by a brief summary of the measured characteristics of test solar cells grown by LTPED. The 17% efficiency target achieved by lab-scale CIGS devices without bandgap modulation, antireflection coating or K-doping is considered to be a crucial milestone along the path to the industrial scale-up of LTPED. The paper ends with a brief review of the open scientific and technological issues related to the scale-up and the possible future applications of the new technology. [ABSTRACT FROM AUTHOR]

CdZnTe crystals were grown by the vertical Bridgman method in closed quartz ampoules. The crystalline quality and the impurity content of these crystals were studied. Several X-ray detectors were cut out of these crystals. The resistivity, emission spectra, \mu \tau product, and spectroscopic characteristics of these detectors were extensively measured and compared with the characteristics of detectors obtained from CdZnTe crystals grown by the boron oxide encapsulated vertical Bridgman technique. The detectors prepared from crystals grown without boron oxide show good \mu \tau value, spectroscopic resolution, and higher reproducibility. The influence of growth method on impurity content and on detector response was discussed. [ABSTRACT FROM AUTHOR]

The realization of low resistivity and stable contacts on p-type CdTe is still challenging, especially if high annealing temperatures must be avoided. In this paper, the electrical characteristics of Sb2Te3 contacts on p-type CdTe single crystals are studied. It is found that the resistivity of the contacts is low and constant with time. [ABSTRACT FROM AUTHOR]

Photoelectrical measurements were taken on InGaP (p+)-GaAs/InGaP-InGaP (n+) multilayers structures, formed by a sequence of nominally undoped InGaP/GaAs quantum wells, interposed between two p+ and n+ InGaP cladding layers. The heterostructures were grown through Low Pressure Metal Organic Vapour Phase Epitaxy, with liquid precursors for the III–V elements and growth conditions optimized for obtaining sharp interfaces and negligible ordering effects in InGaP. The experimental temperature dependence of the photoelectrical signal intensity exhibited peculiarities and anomalies which could lead to erroneous analysis of the perpendicular transport mechanisms, so that they are here critically discussed in the light of a partial depletion of the nominally intrinsic superlattice region of the p–i–n structure. [ABSTRACT FROM AUTHOR]

A great interest is devoted to the development of memories having both high density and low energy consumption for application in personal computers and in automated electronic devices. This target can be achieved if a high dielectric material is obtained. One of the most promising candidates is aluminium oxide, Al2O3, due to its high dielectric constant (∼10), wide band gap (∼8 eV) and thermal stability. Al2O3 can be prepared as an amorphous layer, consequently avoiding strain and electrically active states at the interface between the oxide and the substrate material. In this communication we report on the growth of amorphous Al2O3 layers on n-type silicon. [ABSTRACT FROM AUTHOR]

Single-crystalline InGaAs/GaAs semiconductor micro/nanotubes have been obtained by the strain-driven self-rolling mechanism. This approach combines the advantages of bottom-up (epitaxial growth) and top-down (postgrowth processing) techniques, offering an exceptional opportunity to realize complex three-dimensional nanoarchitectures by using conventional photolithography and wet-etching processes. The method employed to obtain micro/nanotubes with selected orientation and length is described in detail. By means of high-resolution scanning electron microscopy characterization, we show a clear shape difference between single-wall and multiwalls tubes and we discuss it on the basis of strain release, taking into account also possible shape deformations induced during micro/nanotubes drying. We analyse the In-segregation profile in the nominal In0.20Ga0.80As/GaAs bilayer and we show its effect on the actual diameter of the tubes, concluding that a more accurate description of the structure should consider an In0.20Ga0.80As/In0.10Ga0.90As/GaAs trilayer. This work will be useful to set up reliable methodologies for the realization of strain-driven micro/nanotubes with controlled properties, necessary for their implementation in a large number of application fields. [ABSTRACT FROM AUTHOR]

Abstract: A preliminary study of technology and performance of radiation detectors based on bulk semi-insulating (SI) GaAs with P+ blocking electrodes is presented. Detectors with blocking electrode system formed either by P+(GaAs)/N–(SI GaAs) homojunction or P+(Al0.3Ga0.7As)/N–(SI GaAs) heterojunction are prepared. Room-temperature I–V characteristics, measurement and evaluation of pulse–height spectra using 241Am and 57Co radionuclide sources were performed for the characterization of the fabricated detectors. The aim of the study is to verify the possibility to improve the performances of SI GaAs radiation detectors based on the Schottky contact by using the more sophisticated P+–N junction technology. The obtained results and the possibility of future improvements of SI GaAs radiation detectors to be used in digital X-ray imaging are discussed. [Copyright &y& Elsevier]