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In order to effectively utilize the photovoltaic properties of gallium arsenide, its surface/interface needs to be properly prepared. In the experiments described here we examined eight different paths of GaAs surface treatment (cleaning, etching, passivation) which resulted in different external quantum efficiency (EQE) values of the tested photovoltaic (PV) cells. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) examinations were conducted to obtain structural details of the devices. X-ray photoelectron spectroscopy (XPS) with depth profiling was used to examine interface structure and changes in the elemental content and chemical bonds. The photoluminescence (PL) properties and bandgap measurements of the deposited layers were also reported. The highest EQE value was obtained for the samples initially etched with a citric acid-based etchant and, in the last preparation step, either passivated with ammonium sulfide aqueous solution or treated with ammonium hydroxide solution with no final passivation. Subsequent I–V measurements, however, confirmed that from these samples, only the sulfur-passivated ones provided the highest current density. The tested devices were fabricated by using the ALD method.

The structural, optical, and electrical properties of ZnO are intimately intertwined. In the present work, the structural and transport properties of 100 nm thick polycrystalline ZnO films obtained by atomic layer deposition (ALD) at a growth temperature (Tg) of 100–300 °C were investigated. The electrical properties of the films showed a dependence on the substrate (a-Al2O3 or Si (100)) and a high sensitivity to Tg, related to the deviation of the film stoichiometry as demonstrated by the RT-Hall effect. The average crystallite size increased from 20–30 nm for as grown samples to 80–100 nm after rapid thermal annealing, which affects carrier scattering. The ZnO layers deposited on silicon showed lower strain and dislocation density than on sapphire at the same Tg. The calculated half crystallite size (D/2) was higher than the Debye length (LD) for all as grown and annealed ZnO films, except for annealed ZnO/Si films grown within the ALD window (100–200 °C), indicating different homogeneity of charge carrier distribution for annealed ZnO/Si and ZnO/a-Al2O3 layers. For as grown films the hydrogen impurity concentration detected via secondary ion mass spectrometry (SIMS) was 1021 cm−3 and was decreased by two orders of magnitude after annealing, accompanied by a decrease in Urbach energy in the ZnO/a-Al2O3 layers.

In order to effectively utilize the photovoltaic properties of gallium arsenide, its surface/interface needs to be properly prepared. In the experiments described here we examined eight different paths of GaAs surface treatment (cleaning, etching, passivation) which resulted in different external quantum efficiency (EQE) values of the tested photovoltaic (PV) cells. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) examinations were conducted to obtain structural details of the devices. X-ray photoelectron spectroscopy (XPS) with depth profiling was used to examine interface structure and changes in the elemental content and chemical bonds. The photoluminescence (PL) properties and bandgap measurements of the deposited layers were also reported. The highest EQE value was obtained for the samples initially etched with a citric acid-based etchant and, in the last preparation step, either passivated with ammonium sulfide aqueous solution or treated with ammonium hydroxide solution with no final passivation. Subsequent I–V measurements, however, confirmed that from these samples, only the sulfur-passivated ones provided the highest current density. The tested devices were fabricated by using the ALD method.

ZnO implanted with Rare Earth (RE) ions has a potential application as phosphor or in white light sources. The paper discusses the structural, optical and electrical changes caused by Yb, Dy and Pr ions implanted into thin ZnO films grown by Atomic Layer Deposition (ALD). Using channeling Rutherford Backscattering Spectrometry (RBS/c), room temperature photoluminescence (RT PL) technique and Hall effect measurements, it has been shown that the initial damages of the ZnO crystal lattice caused by the rare earth (RE) ion implantation can to a certain extent be removed via post-implantation thermal treatment, provided the fluence is lower than 1.5 × 1015 at.cm−2. A comparison of the structural optical and electrical properties of annealed ALD–ZnO:RE layers with the results of analogous studies performed on thermally untreated RE-implanted films allows us to conclude that properly selected annealing steps allow for a substantial improvement in the conductivity of the layers as well as the intensity of luminescence, which can be attributed to the appearing recrystallization phenomena in the ZnO lattice.

Zinc oxide is nowadays widely investigated in many different science areas. In particular, this wide band gap semiconductor is valued due to its possible use in transparent electronics as TCO (Transparent Conductive Oxide) and/or as ARC (Antireflective Coating). In other applications, ZnO can also play active role in light source devices, UV detectors, solar cells, etc. In this experiment we focused on zinc oxide applicability assessment in solar cell devices. ZnO as well as its Al-doped form AZO (Aluminum doped Zinc Oxide) were examined in view of their use both as TCO and the n-type partner for the p-type gallium arsenide (GaAs) substrate, that resulted in creation of the p-n heterojunction-based photovoltaic device. In order to deposit both ZnO as well as AZO layers, the ALD (Atomic Layer Deposition) method was applied.

Vertical structures based on Pd Schottky contacts to a ZnO/AZO bilayer have been realized and electrically characterized. Following a preliminary annealing study on the separated ZnO and AZO layers the ZnO/AZO bilayer was first annealed at 450 °C for 30 min to reduce the carrier concentration and then functionalized with a H2O2 dip prior to Pd deposition. On the basis of Atomic Force Microscopy, Transmission electron Microscopy and Capacitance vs Voltage measurements it has been found that the H2O2 treatment lowers the surface roughness and creates a ~ 200 nm thick layer formed by ZnO crystallites with grain size ≲ 10 nm embedded into an amorphous matrix with reduced carrier concentration. However, contrary to what previously reported no formation of ZnO2 has been observed. The obtained Schottky contacts showed a rectification ratio ≳ 10 2 at −2 V/+2 V with a detailed analysis based on the differential approach pointing to field enhanced emission from defective channels as the main leaking mechanisms.

Electric measurements were performed on solar cells composed of n-type ZnO nanorods grown by the hydrothermal method on p-type silicon substrate. The nanorods were covered with silver nanoparticles of sizes 20–30 nm and 50–60 nm. The diameters and density of the nanorods and nanoparticles were determined from scanning electron microscopy (SEM) and atomic force microscopy (AFM) images. On top of the structures the ZnO:Al (AZO) layer was deposited as a transparent electrode using the atomic layer deposition (ALD) method. The efficiency of the cells was found to be ∼3.4%, however the sample with larger nanoparticles exhibit better performance. The analysis of the current-voltage (I-V) measurements vs illumination intensity let us conclude that the surface recombination deteriorates their performance. The measurements of capacitance-voltage (C-V) characteristics allowed us to determine the concentration of donors in ZnO and built-in voltage at the ZnO/Si interface. The deep level transient spectroscopy (DLTS) measurements confirmed the presence of defects at the surface as well as deeper in the ZnO nanorods. Obtained results compared with the data reported elsewhere let us conclude that the defect density is much less than in the case of similar heterojunction ZnO/Si solar cells made by other technological methods.

In order to improve the efficiency of a solar cell based on silicon, one must find a compromise between its price and crystalline quality. That is precisely why the knowledge of defects present in the material is of primary importance. This paper studies the defects in commercially available cheap Schottky titanium/gold silicon wafers. The electrical properties of the diodes were defined by using current–voltage and capacitance–voltage measurements. Low series resistance and ideality factor are proofs of the good quality of the sample. The concentration of the acceptors is in accordance with the manufacturer’s specifications. Deep level transient spectroscopy measurements were used to identify the defects. Three hole traps were found with activation energies equal to 0.093 eV, 0.379 eV, and 0.535 eV. Comparing the values with the available literature, the defects were determined as connected to the presence of iron interstitials in the silicon. The quality of the silicon wafer seems good enough to use it as a substrate for the solar cell heterojunctions.

This paper is devoted to the electrophysical diagnostics of the ZnO-based rectifying structures in which the semiconducting oxide layer has been obtained by the low-temperature (80 °C ≤ T ≤ 130 °C) Atomic Layer Deposition (ALD) process. For the growth of examined diodes an organic compound (diethylzinc, DEZn) was used as a zinc precursor. As an oxygen source either deionized (in case of Schottky rectifiers as well as for n-type part of homojunction) or ammonia water (for the p-type layer of homojunction) was applied. In order to improve the basic electrical parameters of these structures (with a particular interest in the rectification (ION/IOFF) ratio) a solution based on inserting the thin dielectric layer (HfO2 or Al2O3) either below the Ag Schottky contact or between the homodiode parts, respectively, has been tested. Through comparing the electrical properties of Ag/HfO2/ZnO/ITO Schottky diodes and ZnO homojunctions as well as modeling their room-temperature current–voltage (I–V) characteristics according to the differential approach it has been proven that the optimal interlayer thickness allowing to achieve the ION/IOFF parameter as high as 104–105 for approximately ± 2 V polarization voltage range is about 2.5–5-nm. Additionally, involving the theoretical studies, the dominant carrier transport mechanisms were identified to be the monopolar injection, tunneling/trapping phenomena occurring in the dielectric layer and bimolecular recombination. The achieved results predestine the examined structures to be applied in the modern electronic devices, where stable in time and good quality diodes are required.

Conventional deep level transient spectroscopy (DLTS) and high-resolution Laplace DLTS techniques were used to study electrical properties of deep-level defects in dilute GaNAs epitaxial layers grown by atmospheric-pressure metalorganic vapourphase epitaxy (APMOVPE) on the GaAs substrate. Three samples with nitrogen concentrations of 1.2 %, 1.6 % and 2.7 % were investigated. In DLTS and LDLTS spectra of the samples, four predominant electron traps were observed. On the basis of the obtained electrical parameters and previously published results, one of the traps was associated with N-related complex defects, while the other traps with common GaAs-like native defects and impurities, called EL6, EL3 and EL2.

The impact of hydrogen in ZnO is revealed by combining reaction dynamics calculations with temperature dependent Hall (TDH), photoluminescence, and secondary ion mass spectrometry measurements performed on H, 2H, and He implanted ZnO. H and 2H box profiles with a concentration ranging from ∼ 3 × 10 17 cm − 3 to ∼ 10 19 cm − 3 and He to produce as much as damage as in the [H] ∼ 3 × 10 17 cm − 3 case were implanted in the samples. The formation of Li lean regions has been observed for [ 2H] < 10 19 cm − 3 after annealing at 400 °C. This is attributed to Li i presence consequent to the diffusion of Zn i created during the H/ 2H implantation process. Results extracted from the TDH measurements performed prior to the annealing at 400 °C evidence that Li i contributes to an increase in carrier concentration up to ∼ 10 17 cm − 3 by providing a donor level with an activation energy of ∼40 meV and thus is very close to the value of ∼47 meV expected for H in the oxygen site. The reaction dynamics analysis evidences that the amount of Li i introduced is decreasing at higher H implantation doses as a result of increasing V Zn and H-V Zn retrapping, reactions in which Li i is competing with H. Overall, due to Li i formation as well as the presence of Al the maximum percentage of the implanted H or 2H acting as a donor in the investigated range is found to be ≲ 2%, which is considerably lower than previously reported.

The theoretical approach towards improving the photovoltaic response of n-ZnO/p-Si heterojunctions proposed by Knutsen et al. [Phys. Status Solidi A 210 (2013) 585–588] has been experimentally tested. AZO/n-Zn(1−x)MgxO layers were deposited at 160 °C on p-Si substrates by atomic layer deposition (ALD) with magnesium concentration in the 0–4 at% range. The examined devices showed a reduction of the conduction band offset from (0.63±0.03) eV to (0.48±0.03) eV. This decrease leads to a diminishing impact of recombination centers at the interface between zinc oxide based layers and silicon substrate, when the Mg content is below ~1.6 at%. In this range, the overall photovoltaic efficiency increased from ~3.7% to ~6.0%. As a next step, we tested solar cells with similar magnesium concentration in the Zn(1−x)MgxO layer, but deposited at 300 °C. Due to the higher deposition temperature, a further 1.1% increase in efficiency has been obtained. So far, this is the highest reported efficiency for a ZnO/Si heterojunction grown by ALD method, thus experimentally confirming the validity of the approache s here studied for raising the efficiency of heterojunctions solar cells based on n-ZnO/p-Si, while significantly reducing the fabrication complexity respect to conventional Si based devices as emphasized by Hussain et al. [Sol. Energy Mater. Sol. Cells 139 (2015) 95–100].

Zinc oxide (ZnO) films were used in silicon-based photovoltaic (PV) structures both as an n-type partner to p-type Si and (on top) as a transparent electrode (as a so-called TCO film). Photovoltaic response of such PV structures depends on the electrical properties of n-ZnO films as well as p-Si (100) substrates. The ZnO-based TCO films were deposited by an Atomic Layer Deposition (ALD) method. The films show a high electron concentration (~10 20 cm −3 ) and a relatively high electron mobility (>10 cm 2 /V s). Considering Si, we used fairly cheap commercial substrates with 360 µm thickness, i.e., not optimized for PV cells applications. The best results were obtained for Si substrates with a moderate hole concentration (~10 15 cm −3 ) and resistivity of 10 Ω cm. The photovoltaic efficiency achieved is 4.4%, with the possibility of further improvement.

We report on the properties of photovoltaic (PV) structures based on thin films of n-type zinc oxide grown by atomic layer deposition method on a cheap silicon substrate. Thin films of ZnO are used as n-type partner to p-type Si (110) and, when doped with Al, as a transparent electrode. PV structures with different thicknesses of ZnO layers (from 600 nm to 1600 nm) were deposited to determine the optimal performance of PV structures. The best response we obtained for the structure with ZnO layer thickness of 800 nm. The so-obtained PV structures show 6% efficiency.

Properties of UV detector based on ZnO nanorods, grown by a hydrothermal method, are discussed. The innovative growth technology was used to produce ZnO nanorods. It is characterized by a much higher growth rate, than reported (till now) in the literature, and a very low costs (both of technology and materials). Importantly, ZnO nanorods grown by this method are free from oxygen vacancies. Despite the fact that detector proposed by us is not based on a single nanorod, but on a whole array of nanorods, it is very sensitive. The detector shows sensitivity of 20 mW/m2 (2 µW/cm2) upon UV illumination. Due to a high energy band gap of zinc oxide and a high purity of the obtained nanorods visible light is not detected. The resistivity/current changes are proportional to illumination intensity, i.e., detector response scales with the intensity of UV light. The observed changes of the detector resistivity relate to surface reactions generated upon an illumination. Importantly, detector does not need annealing or cleaning to reset to an initial state.(© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

High quality heterojunctions based on dual acceptor doped ZnO:(As,Sb) films grown on n-type GaN templates were used for UV detector application. Photodetectors made on the obtained diodes appeared to have a high selectivity in the UV spectral range. Photocurrent measurements revealed a very narrow response window of ∼12 nm only. The difference between the dark and bright current was large and the ratio of these currents was about 103. The response time of the detectors is shorter than 1 ms.

Selected properties of photovoltaic (PV) structures based on n-type zinc oxide nanorods grown by a low temperature hydrothermal method on p-type silicon substrates (100) are investigated. PV structures were covered with thin films of Al doped ZnO grown by atomic layer deposition acting as transparent electrodes. The investigated PV structures differ in terms of the shapes and densities of their nanorods. The best response is observed for the structure containing closely-spaced nanorods, which show light conversion efficiency of 3.6%.

Arsenic-doped ZnO films were formed by thermal annealing of epitaxial ZnO films grown by Atomic Layer Deposition (ALD) in arsenic atmosphere at temperature 850–950 °C. X-ray photoelectron spectroscopy (XPS) studies of the ZnO:As films revealed the complex As3d core level spectra formed by three components located at about 41 eV, 45 eV and 47.5 eV below the Fermi level. The As3d component at binding energy (BE) of 45 eV was found to be correlated with the acceptor bound A°X exciton state observed in low temperature photoluminescence. This observation strongly supports the previously postulated assumption that the origin of the 45 eV component of the As3d spectra can be ascribed to arsenic atoms in As Zn –2V Zn complexes formed as a result of high temperature annealing. This assumption is also supported by the evident valence band shift towards the Fermi level in the ZnO:As film annealed at 950 °C.

In this paper we report on the optical and electrical studies of single GaAs1−xNx epitaxial layers grown on GaAs substrates by means of atmospheric pressure metal organic vapour phase epitaxy (APMOVPE). Three kinds of samples with 1.2 %, 1.6 % and 2.7 % nitrogen content were studied. Optical properties of the layers were investigated with the use of room temperature transmittance and reflectance measurements. Subsequently Schottky Au-GaAs1−xNx contacts were processed and characterized by current-voltage (I-V) and capacitance-voltage (C-V) measurements within 80–480 K temperature range. From the I-V and C-V characteristics the ideality factor, series resistance and built-in potential were determined. Obtained diodes can be used for further studies on defects with the use of DLTS method.

We present results of a resonant photoemission study of (Zn,Co)O films with Co content between 2% and 7%. The films were grown by Atomic Layer Deposition (ALD) at low temperature of 160 degrees C and show fully paramagnetic behavior. The Co ions are uniformly distributed in the ZnO matrix and are free of foreign phases and metal accumulations as indicated by TEM data. The electronic structure of (Zn,Co)O films was studied by Resonant Photoemission Spectroscopy across the Co3p-Co3d photoionization threshold. We have observed that the resonant enhancement of the photoemission intensity from the Co3d shell is not the same for samples with different cobalt content. We suggest that the Co3d contribution to the valence band depends on both Co and H content. (C) 2011 Elsevier Ltd. All rights reserved. (Less)

In the present work we report on the monocrystalline growth of (00.1) ZnO films on GaN template by the Atomic Layer Deposition technique. The ZnO films were obtained at temperature of 300 °C using dietylzinc (DEZn) as a zinc precursor and deionized water as an oxygen precursor. High resolution X-ray diffraction analysis proves that ZnO layers are monocrystalline with rocking curve FWHM of the 00.2 peak equals to 0.07°. Low temperature photoluminescence shows a sharp and bright excitonic line with FWHM of 13 meV.

This paper reports on the electrical and optical properties of zinc oxide thin films grown at the temperature range between 160 and 240 °C by the atomic layer deposition method using diethylzinc (Zn(C 2 H 5 ) 2 , DEZn) and deionized water precursors. Silicon and glass were used as substrates for the ZnO growth. These films were characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM), low temperature photoluminescence (LT PL) and low temperature Hall effect measurements. This analysis revealed that all the obtained as-grown ZnO layers are fairly smooth (with a roughness RMS parameter less than 4 nm), show a metallic-like conductivity, exhibited a carriers' concentration (n) of 10 19 -10 20 cm -3 which was found to be practically independent of temperature between 7 and 300 K. From the LT PL spectra, it was established that the carriers' concentration is nearly inversely proportional to the intensity of the LT PL edge emission peak. These observations, together with the fact that the Hall mobility slightly increases at higher temperatures, indicate the existence of a competitive scattering mechanism (on grain boundaries as well as on ionized impurities). However, ionized impurity scattering seems to be the dominant factor limiting the carrier mobility in the discussed case. Moreover, the results suggest that efficient non-radiative Auger processes are responsible for the observed photoluminescence (PL) quenching in the samples with higher electron concentration.

We report on properties of low-temperature (LT) ZnO films grown by the atomic layer deposition method with diethylzinc (DEZn) precursor. It is shown that the ZnO thin film crystallographic orientation, quality of the surface, and optical properties depend on the main growth parameters like temperature, pulsing, and purging time and thus can be varied in controllable manner. All the presented results were obtained for ZnO layers grown at temperature between 90 and 200 degrees C. (C) 2008 Elsevier B.V. All rights reserved.

Properties of ZnO films grown by atomic layer deposition at low temperature are described. By selecting appropriate precursors and their pulses we obtained films with controlled electrical properties - from heavily n-type to p-type. Parameters of constructed Schottky and p-n junction are good enough for their application in a new generation of memory devices with cross-bar architecture. (C) 2008 Elsevier B.V. All rights reserved.

We report on fabrication of hybrid inorganic-on-organic thin film structures with polycrystalline zinc oxide films grown by atomic layer deposition technique. ZnO films were deposited on two kinds of thin organic films, i.e. pentacene and poly(dimethylosiloxane) elastomer with a carbon nanotube content (PDMS:CNT). Surface morphology as well as electrical measurements of the films and devices were analyzed. The current density versus voltage (I–V ) characteristics of ITO/pentacene/ZnO/Au structure show a low-voltage switching phenomenon typical of organic memory elements. The I–V studies of ITO/PDMS:CNT/ZnO/Au structure indicate some charging effects in the system under applied voltages.

Optical and magnetic properties of ZnMnO fllms are discussed based on the results of cathodoluminescence, photoluminescence, and magneto-photoluminescence investigations. We show that photoluminescence/cathodoluminescence emissions are strongly quenched and become in-plane inhomogeneous in samples with increased Mn fractions. Strong polarization of photoluminescence is observed, even though excitonic lines do not shift and are not split at magnetic flelds up to 6 T.

ZnO thin films were grown on silicon substrate by atomic layer deposition method. We explored double-exchange chemical reaction and used very volatile and reactive diethylzinc as a zinc precursor. These enables us to obtain zinc oxide thin films of high quality at extremely low growth temperature (90−200◦C). The films are polycrystalline as was determined by X-ray diffraction and show flat surfaces with roughness of 1–4 nm as derived from atomic force microscopy measurements. Photoluminescence studies show that an edge emission of excitonic origin is observed even at room temperature for all investigated ZnO layers deposited with the diethylzinc precursor.

Zinc oxide crystals were grown by CVT contactless technique and thermally annealed in the air, nitrogen or oxygen atmospheres, or zinc or arsenic vapours. Wide ranges of annealing times and temperatures were applied. The variety of morphology and quality of the crystal surface was investigated by AFM and XRD. It was found, that thermal annealing in the air, nitrogen, oxygen and zinc resulted in similar evolution of the crystal surface, although there are observed differences in the rate of the changes. The annealing in zinc vapour resulted in roughness (RMS) lower than 1 nm. The annealing in arsenic vapour leads to degradation of the crystal surface. The improvement of the surface was not observed in case of thermal annealing of the rough ZnO surfaces obtained by ALE homoepitaxy on the smooth CVT as-grown ZnO surfaces.

Monocrystalline films of sphalerite-type ZnSe were grown on GaAs(100) substrates from elemental Zn and Se precursors by atomic layer epitaxy in a gas flow system. Due to color mixing of band edge and deep defect-related emissions these layers emit intensive white light. Depth profiling cathodoluminescence indicates that green and red emissions mostly come from disordered regions of the films, close to the ZnSe/GaAs interface. We tested a possibility of tuning of chromaticity coordinates and of color temperature of the emission. We found that the chromaticity parameters (color perception) can be tuned by either regulating the appropriate accelerating voltage of electrons or current density of primary electrons in cathodoluminescence investigations. These properties of ZnSe films make them suitable for some practical applications as white light sources.

Magnetic, structural, and optical properties of ZnMnO films grown with atomic layer epitaxy are discussed. Atomic layer epitaxy films were grown at low temperature using organic zinc and manganese precursors. From magnetometry and electron spin resonance investigations we conclude that lowering of a growth temperature significantly limits formation of Mn precipitates and inclusions of different foreign phases of manganese oxides to ZnMnO host.

The electronic band structure of Mn/ZnTe(110) (1×1) has been studied by angle-resolved photoelectron spectroscopy. The sets of spectra were acquired for the clean surface and after in situ deposition of 0.4 ML of Mn, in order to compare the band structures and to reveal changes brought about by the presence of Mn. The experimental band structure diagram of Mn/ZnTe along the Γ−K direction in the Brillouin zone has been derived from the experimental data. Indications of interaction between the Mn 3d states and sp bands of the semiconductor are discussed.

The Mn/ZnO(0001) system was investigated by synchrotron radiation photoemission. The Mn/ZnO interface with 4 ML of manganese deposited onto the ZnO surface was annealed up to 500◦C. No Mn capping layer was found at the surface after annealing as was confirmed by scanning Auger spectroscopy experiment. We used a resonant photoemission to extract the Mn3d partial density of states in photoemission spectra. The Mn3d states contribute to the electronic structure of the system within 10 eV of the Fermi level. They show three features: a main peak at 3.8–4.5 eV, a valence structure at the top of the valence band (1–3 eV), and a broad satellite situated between 5.5 and 9 eV below EF. The satellite/main branching ratio was determined to be 0.43, which is a fingerprint of strong hybridization between the Mn3d electrons and the valence band of the crystal. The hybridization effect in Zn1−xMnxO surface alloy is comparable to Zn1−xMnxS and much higher than in Zn1−xMnxSe, Zn1−xMnxTe, and Ga1−xMnxAs semimagnetic compounds.

Atomic layer epitaxy (ALE) was applied to grow thin films of monocrystalline and polycrystalline ZnO. Monocrystalline films were obtained only for GaN/Al2O3 substrates, whereas use of sapphire, silicon or soda lime glass resulted in either 3D growth mode or in polycrystalline films showing preferential orientation along the c axis. Successful Mn doping of ZnO films is reported, when using organic Mn precursors. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The electronic structure of monocrystalline ZnTe was investigated for a clean, relaxed ( 110)-(1 x 1) surface and for the same surface after sequential deposition of Mn atoms. The resonant (Fano-type) photoemission technique was applied. The spectra were measured as energy distribution curves and in the constant initial state mode, for the valence band and Zn 3d core level. At very low Mn coverage (θ < 0.15 nm), manganese interaction with the crystal surface results in creation of ternary alloy Zn 1-x Mn x Te(110) surface. Further increasing of Mn deposition leads to formation of metallic manganese islands on the surface. The successive annealing leads to Mn atoms diffusion and to formation of Zn 1-x Mn x Te at the surface region.

Atomic layer epitaxy (ALE) of ZnO on a GaN template was performed in a low-pressure gas flow system using ZnCl2 and O2 precursors, and the evidence of monocrystallinity of an ALE-grown ZnO film is presented. The growth is achieved under the pressure of about 5 mbar with 480 °C substrate temperature and the ZnCl2-source temperature of 390 °C. According to the AFM analyses, the film surface exhibits a low roughness value of 0.45 nm RMS, which fulfills the expectations with respect to high morphological quality of the ALE products. The structural properties of the produced ZnO are characterized by means of X-ray diffraction methods based on wide range 2θ/ω scans and high-resolution studies of 00.2 and 11.4 reciprocal lattice points. Lattice parameters for ALE-grown ZnO layer are a = 0.3253(1) nm and c = 0.52060(5) nm, as derived from the high-resolution data. The mosaicity level of the GaN template layer is reproduced in the grown ZnO film.

Zinc oxide is a II–VI semiconductor material which is gaining increasing interest in various fields such as biology, medicine or electronics. This semiconductor reveals very special physical and chemical properties, which imply many applications including a transparent electrode in solar cells or LED diodes. Among many applications, ZnO is also a prospective material for sensor technology, where developed surface morphology is very advantageous. In this work we present ZnO nanowires growth using atomic layer deposition method. ZnO nanowires were obtained using controlled physical properties. As a substrate we used gallium arsenide with gold-gallium eutectic droplets prepared on the surface at high temperature. To obtain the eutectic solution there was put a gold thin film on GaAs through the sputtering and then we annealed the sample in a nitrogen gas flow. The so-prepared substrate was applied for growth of ZnO nanowires. We used deionized water and zinc chloride as oxygen and zinc precursors, respectively. The eutectic mixture serves as a catalyst for the ZnO nanowires growth. Au–Ga droplets flow on the front of ZnO nanowires. Scanning electron microscopy images show ZnO nanorods in a form of crystallites of up to 1 μm length and a 100 nm diameter. It is the first demonstration of the ZnO nanowires growth by atomic layer deposition using the vapour–liquid–solid approach.

We present the results of photoemission studies on (0 0 0 1 ) (N-polar) surfaces of bulk gallium nitride crystals. The procedures that yield clean and well-ordered (0 0 0 1 ) (1×1) surfaces were developed and tested. The surface crystallinity was assessed by low-energy electron diffraction. Angle-resolved photoemission spectroscopy with synchrotron radiation was used to determine the valence-band electronic structure of GaN along the Γ – Δ – A direction of the Brillouin zone. The band structure derived from our experimental data is compared with the results of recent band structure calculations.

We demonstrate experimental results on p-type ZnO films grown by atomic layer deposition (ALD) and co-doped with aluminum and nitrogen (ANZO). The films were obtained at low temperature (100 °C) with different N to Al ratio and show conductivity type, which depends on the N and Al content. We applied the x-ray photoelectron spectroscopy in order to get insight into a chemical nature of dopants and we found three pronounced contributions of the N1s core level which appear at binding energies of 396.1, 397.4 and around 399 eV. Based on ANZO and undoped ZnO films, both grown by the ALD technique, the ZnO homojunction was obtained in one technological process without any post-growth high temperature processing. The rectification ratio as high as 4 × 104 at ± 2 V was achieved when an ultrathin Al2O3 layer was inserted between p- and n-type ZnO and a n-type ZnO buffer layer deposited on an insulating Si substrate was applied.

The new trend in semiconductor technology is search of new materials, which could replace silicon in specialized applications. One of them is zinc oxide (ZnO), a II-VI semiconductor. In this work we show how to obtain at relatively low temperature monocrystalline layers of ZnO using atomic layer deposition (ALD) method with reactive dimethylzinc (DMZn) and diethylzinc (DEZn) precursors. ZnO films were deposited on gallium nitride substrates at 300°C. We compare the results obtained for these two organic zinc precursors. High resolution X-ray diffraction analysis proves that our ZnO layers are monocrystalline with FWHM of (00.2) peak 250 arcsec for DEZn and 335 arcsec for DMZn precursors.

In this paper we report on the low-temperature growth (T"s=30-250^oC) of zinc oxide thin films by atomic layer deposition method using two different organic zinc precursors: diethylzinc and (for comparison) dimethylzinc, and deionized water as an oxygen precursor. An evident influence of growth temperature and precursors' doses on electron concentration and Hall mobility of obtained zinc oxide layers is presented. The lowest achieved room-temperature electron concentration was at the level of 10^1^6cm^-^3 with mobility up to 110cm^2/Vs.

We studied epitaxial growth conditions of II—VI semiconductors on (110) substrates, which is indispensable for fabrication of T-shaped quantum wire structures. We experimented with different types of (110)-oriented substrates and monitored the surface quality of deposited layers in situ by reflection high energy electron diffraction and ex Situ by photoluminescence. The aim of this work is to find optimum growth conditions of II—VI compounds on a cleaved edge of a superlattice as required by the overgrowth method.

ZnO films with high conductivity are obtained by atomic layer deposition for the application in solar cells based on CdS/CdTe/Cu2S films. The parameters of solar cells with ZnO electrode are compared with the ones with Mo. The advantages of ZnO electrode are discussed.