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Two-step synthesis of Y2O3:Eu nanostructures was performed. It includes microwave driven hydrothermal and calcination stages. Performed route results in crystallization of Y4O(OH)9(NO3):Eu crystals initially, then Y2O3:Eu crystals after calcination. Arranged Eu contents in relation to overall cation quantity were set to 2 mol%, 10 mol% and 20 mol%. Varying europium concentrations influence habit of obtained Y4O(OH)9(NO3):Eu crystals from needle-like to plate-like and as a result, also shapes of final Y2O3:Eu nanostructures. Additionally, certain amount of Eu2+ ions was detected in as-grown material using laser spectroscopy and decay kinetics measurements. Obtained material was calcined at 1200 °C in the air, which results in oxidation of Eu2+ ions and crystallization of small number of cubic Eu2O3 nanocrystals. Characterization of obtained materials was performed using XRD, SEM, TEM, EDX, CL, Raman and photoluminescence spectroscopy.

Europium doped hafnium dioxide nanoparticles were crystallized using biologically friendly microwave hydrothermal method and employed in observation of small rodents tissues. Main solvent in synthesis is water, in consequence nanoparticles are found surrounded by thin hydroxide layer. Size of the nanoparticles is controlled by temperature of calcination. 1200 °C heating causes drop of luminescence intensity, explained as damage of high symmetry surface emission centers in the nanocrystals. On the other hand, growth of crystallites increases intensity of X-ray and electron beam excited luminescence. This makes them promising activator in photodynamic therapy.

Zinc oxide nanoparticles were synthesized with microwave hydrothermal technique and tested as luminescent contrast for biological imaging. Luminescence was activated by Eu3+ ions embedded in the nanoparticle matrix in the increasing concentrations of 1, 5 and 10 %mol. It was found that europium did not create a separate crystalline phase up to the concentration as high as 5 %mol. However, Eu3+ ions did not substitute Zn2+ in the host lattice, but allocated in the low symmetry environment. It was proposed that europium was locating in the inter-grain space or on the surface of nanoparticles. The luminescence intensity in ZnO:Eu, as well as the size of particles, increased with the Eu ion concentration. Moreover, in 10 %mol Eu sample, the separate phase of Eu-hydroxide was identified with crystals of micrometre length. Interestingly, in vivo study revealed, that contrary to the in silico experiments, following gastric gavage, the brightest nanoparticle-related luminescence signal was observed at 1 %mol. concentration of Eu. Since the alimentary uptake of nanoparticles was related to their size, we concluded that the increase in luminescence at 5 and 10 %mol. Eu concentrations was associated with the largest ZnO:Eu and Eu-hydroxide particles that did not cross the gastrointestinal barrier.

In recent years, a series of investigations has been devoted to a possibility of using crystals based on CdTe with addition of magnesium (Mg) for X and gamma radiation detectors. Since we have had wide technological possibilities of preparing crystals and investigating their properties, we performed crystallizations of the crystals mentioned above. Thereafter, we investigated selected properties of the obtained materials. The crystallization processes were performed by using the Low Pressure Bridgman (LPB) method. The elements used: Cd, Te, Mg were of the highest purity available at present. In order to obtain reliable conclusions the crystallization processes were carried out at identical technological conditions. The details of our technological method and the results of the investigation of physical properties of the samples are presented below.

In this paper we present luminescence results of nitrogen doped and undoped ZnO layers grown at 100 °C by atomic layer deposition and post grown annealed. A comprehensive analysis of the excitonic peaks as well as the controversial band at ~3.32 eV is presented. Based on temperature dependent luminescence analysis we identified PL peaks originating from donor and acceptor bound excitons D°X and A°X. It has been found that two acceptor-related PL peaks observed between 3.30 and 3.32 eV reveal different temperature behavior. The emission at 3.302 eV has been assigned to donor-acceptor pairs (DAP), whereas the emission at 3.318 eV to free electrons to acceptor transition. Activation of an acceptor as a result of high temperature annealing is reflected in PL spectra as an appreciable increase of the DAP emission. The binding energies of existing donors and acceptors have been also calculated and the possible origin of the donors and acceptors in ZnO and ZnO:N layers grown at low temperature was proposed. Furthermore, the planar cathodoluminescence images discover that acceptor related emission comes from whole grains area.

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.

Well-aligned ZnO nano/micro-rods with identical crystallographic orientation were synthesized on a c-plane GaN template, using a microwave-assisted hydrothermal method at 50 °C for duration of 2 min. The ZnO nanorods exhibited true epitaxial growth, in contrast to most of the previously reported methods, which involve nucleation on a ZnO buffer layer pre-deposited on the substrate. Homogeneous in-plane alignment as well as the c-axis orientation were confirmed by X-ray diffraction measurements and TEM analysis. More importantly, in the photoluminescence spectra of the nanorods a strong, narrow excitonic emission and an extremely weak deep level emission were observed, indicating high optical quality. The diameter was controlled by adjusting pH of the solution used in the growth process. The main achievement of the research was the opportunity to obtain oriented, high quality ZnO nano/microrods, using a surprisingly quick, cheap, and safe growth process, without the use of toxic substances or ultra-high purity compounds.

In recent years, a series of investigations has been devoted to a possibility of using crystals based on CdTe with addition of magnesium (Mg), selenium (Se), or manganese (Mn) for X and gamma radiation detectors. In the literature there are contradictory data with respect to the segregation of Mg in (Cd,Mg)Te and Se in Cd(Te,Se) and to the possibility of obtaining materials with a homogeneous composition without grains and twins. We have wide technological possibilities of preparing crystals and investigating some of their properties. Thus, we performed crystallizations of (Cd,Mg)Te, Cd(Te,Se), (Cd,Mn)(Te,Se), and (Cd,Mn)Te compounds. The aim of our studies was to check whether any of the investigated materials may be easily obtained by the Low Pressure Bridgman (LPB) method in the form of large, homogeneous, high resistivity single crystals with as few as possible twins, subgrains, and tellurium inclusions. The crystallization processes were performed by using the LPB method. The elements used: Cd, Te, Mn, Mg, and Se were of the highest purity available at that time. In order to obtain reliable conclusions the crystallization processes were carried out under identical technological conditions. The details of our technological method and the results of the investigation of physical properties of the samples are presented below.

The use of nanoparticles in medicine is a rapidly growing research field with numerous potential applications, especially in the field of cancer diagnosis and therapy. Nanoparticles can be intrinsically diagnostic of therapeutic, or they can be conjugated with diagnostic or therapeutic compounds. Nanoparticles may also passively or actively target tumor cells specifically using the enhanced permeation and retention (EPR) effect, or the addition of targeting ligands to their surface. This may provide a diagnostic or/and therapeutic tools to target primary as well as metastatic tumors. The transport, distribution and toxicity of nanoparticles depends greatly on their size and composition, thus every new formulation needs to be extensively researched. This work was focused on the development of Tb-doped ZrO2 nanoparticles (NPs) for application in cancer imaging. Obtained nanoparticles were below 10 nm with very low influence of Tb concentration on size. Terbium stabilization of ZrO2 had influence on the luminescence properties of obtained material. Partially stabilized zirconium dioxide exhibited broad host related emission peaking at 500 nm, disappearing with the terbium content. We confirmed alimentary absorption and wide distribution of luminescent ZrO2:Tb nanoparticles in mice with their gradual accumulation in the experimentally induced mammary cancers. Furthermore, a high concentration of NPs was found within the lung metastases as opposed to healthy lung tissue, where no NPs-related signal was observed.

Epitaxial ZnO films implanted with ytterbium have been studied by combination of channeling Rutherford backscattering spectrometry and Hall measurements. This approach is able to shed more light onto the difficult problem of optical activation of Yb implanted into the ZnO lattice. ZnO films grown by atomic layer deposition on a GaN/Al 2 O 3 substrate were implanted with Yb + ions to the fluences of 5 × 10 14 , 1 × 10 15 and 5 × 10 15 at./cm 2 . RBS/c spectra show that for as implanted samples the fraction of implanted Yb ions occupying substitutional lattice positions amounts to 72%, 54% and 22%, respectively. Annealing under an ambient atmosphere at 800 °C leads to a partial recovery of the crystal lattice but also substantially reduces substitutional fraction of Yb atoms. Photoluminescence studies on the as-implanted samples revealed a very weak luminescent peak in the near-infrared region, which slightly increases with a fluence. The annealing process leads to optical activation of Yb 3 + ions and significantly increases the previously observed the near-infrared inter-ionic emission. The results obtained from Hall measurements indicate that after implantation Yb ions are mainly in the 2 + state and are transformed to the optically active 3 + state as a result of annealing. It suggests that the process of optical activation via annealing is related not only to lattice recovery, but also to Yb diffusion from substitutional to interstitial positions, where Yb ions are in the optically active 3 + state.

Currently, the first generation of silicon solar cells is dominating the photovoltaic market. Silicon cells are produced by various methods, which employ either crystalline or multi-crystalline substrates. However, both these manufacturing processes are expensive and potentially harmful to the environment and health. One example of this is that the surface is given its texture in a highly corrosive water solution of nitric and hydrofluoric acid. Additionally, both the diffusion and manufacturing of p-n junction and of metal contacts are associated with very high temperatures. This prompted us in our search for cheaper and more environmental friendly technologies. In this work, we discuss the possibility of producing components of photovoltaic cells by employing atomic layer deposition and hydrothermal technologies. This does not require the use of hazardous chemicals and high temperatures. The maximum efficiency of zinc oxide/silicon solar cells is 14% and 10% for textured and planar structures, respectively. A environmentally-friendly and simple procedure is thus being proposed, which, together with its relative efficiency, makes it an attractive alternative to the present procedure.

Scratches and constant abrasive wear can result in zinc oxide (ZnO) and aluminum doped zinc oxide (ZnO:Al) layers that render many devices impracticable to use. Currently, the ZnO and ZnO:Al layers are widely used as transparent conductivity oxide (TCO). The top and/or bottom electrodes based on ZnO and ZnO:Al were used in organic light-emitting diodes (OLED), organic and perovskite solar cells in order to replace expensive indium tin oxide (ITO). Consequently, knowledge of the frictional properties of the ZnO layer is a necessity for many scientists. In this study, the tribological properties of zinc oxide that was formed by the Low Temperature Atomic Layer Deposition (LT ALD) method were investigated. ALD-layers (ZnO and ZnO:Al) were deposited on a glass substrates in pre-selected conditions in order to achieve films appropriate for the application of photovoltaics. The results indicate a good adhesion of the films to the substrate. The layers were abraded during friction with Al 2 O 3 ball and their wear intensity depend on hardness of the film/substrate system. The friction coefficient of ZnO film reached value 0.1 and was higher than friction coefficient of ZnO:Al film equal 0.08. The tribological properties of these films are compared with those reported for bulk ZnO and those films deposited by sputtering.

Asymmetric ZnO/ZnMgO double quantum well (QW) structures grown on non-polar m-plane ZnO bulk substrates are investigated. Pairs of 2 and 5 nm wide ZnO QWs were grown on ZnMgO buffer/barrier layers with Mg concentrations over 20%. The QWs are separated with 7 nm or 20 nm ZnMgO barriers. Temperature dependent photoluminescence (PL) and low temperature cross-sectional cathodoluminescence allowed to identify the origin of the observed spectral lines. Well resolved and narrow luminescence lines due to localized and free excitons are observed, confirming excellent quality of the structures. The results of luminescence studies suggest that at the barrier width of 7 nm coupling between the wells enhances excitonic emission in 5 nm well via tunneling of charge carriers from 2 nm to 5 nm QW. No trace of inter-well coupling in a structure with a 20 nm thick barrier is observed. It is found that the binding energies of excitons in 2 and 5 nm wells are 52 and 101 meV, respectively. Such large enhancement of the binding energies is due to the quantum confinement in the wells.

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.

ZnO:Al-hydroquinone (AZO-HQ) films were grown on poly(ethylene terephthalate) (PET) substrates by atomic and molecular layer deposition (ALD/MLD). Organic contents in the films varied from 0 to ≈4 vol%. Structural and electrical investigations of the films were carried out. Electrical measurements were performed under film bending. The piezoresistive effect in the films with different organic contents was observed and described. Critical bend radius, critical strain, and piezoresistive coefficient values were related to the film microstructure. The piezoresistivity was found to be enhanced for the deformations of ZnO crystallites along the a-axis whereas higher critical strain was influenced by long crystallites oriented in the deformation direction. AZO-HQ films having 2 vol% of the organic content are characterized by the lowest critical bend radius and the highest critical strain among the films under study. Keywords: Zinc oxide, Molecular layer deposition, Electrical properties, Piezoresistive effect

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.

Europium doped ZnO nanopowders made by microwave hydrothermal method are investigated. As zinc oxide precursor zinc nitrate(V) hexahydrate (Zn(NO3)2·6H2O) was used. Two types of nanopowder samples are examined: as grown and annealed at 750 °C in air atmosphere. We investigate the structural, morphological and optical prosperities of europium doped ZnO. Results of scanning electron microscopy, X-ray diffraction, photo- and cathodoluminescence investigations and also CIE1961 chromaticity diagram are presented.

Microwave hydrothermal growth of Y2O3 crystallites results in needle-shaped aggregates of μm length. Thermal treatment has little influence on the material microstructure, but significant impact on the nanometric level. Nanoparticles doped with europium show an intense red luminescence, related to the 5D0 → 7F2 transition of Eu3+ ions. The luminescence intensity increases with the calcination temperature and is accompanied by increasing size of Y2O3:Eu crystallites. EPR studies show the absence of Eu2+ related signals in the material. Y2O3:Eu nanoparticles crystallized via a microwave hydrothermal method were employed as luminescent biomarkers in mice. The initial tests confirmed their applicability as biological markers. Persorption of the Y2O3:Eu nanoparticles after IG in the adult mouse duodenum, brain and liver is reported.

Thermally induced crystallization of cubic Eu2O3 obtained with the microwave hydrothermal method has been investigated. The starting material crystallized in the form of needle-shaped agglomerates of nanocrystalline hexagonal Eu(OH)3. Thermal treatment up to 800 °C induced the crystallization of cubic Eu2O3, after further calcination at 1200 °C in the air a monoclinic phase appeared. The phase transformation caused abnormal reduction of Eu3+ ions, related to the oxygen vacancy creation during sintering of the oxide crystallites. The crystallization process of cubic Eu2O3 occurred within the agglomerates without change of their shapes. The cubic form exhibited bright emission of Eu3+ related luminescence with intensity increasing with the size of crystallites.

In this paper a new generation of non-toxic nanoparticles based on the zirconium oxide doped with 0.5%Tb and co-doped by the range of 0–70% with Y was evaluated for the use as a fluorescent biomarker of neuronal trafficking. The ZrO 2 :Tb nanoparticles were created by microwave driven hydrothermal method. Influence of the yttrium content and thermal processing on the Tb 3+ related luminescence emission was discussed. The higher intensities were achieved, when host was cubic and for the nanoparticles with 33 nm. Presence of yttrium was associated with the energy coupling of the host and dopant, wide excitation band is present at 309 and 322 nm before and after calcination respectively. For the experiment on living primary neurons, nanoparticles doped with 0.5%Tb and 7%Y were chosen based on their luminescence emission intensity. Recently transfer of the nanoparticles through the barriers in the organism including blood–brain barrier following their alimentary absorption was confirmed (Godlewski and Godlewski, 2012). This raised the possibility of the nanoparticle application as a tool in the neuroscience, and the question of potential mechanisms of nanoparticle turnover in neurons. Concentration of 0.001 mg/ml of ZrO 2 :0.5%Tb 7%Y in growth medium was added to the primary murine culture medium, and the intracellular trafficking of nanoparticles was observed following 15 min pre-incubation period. ZrO 2 :0.5%Tb 7%Y nanoparticles were dynamically absorbed by the neurons and the dynamic passage of transport vesicles containing ZrO 2 :0.5%Tb 7%Y nanoparticles was observed along the neuronal processes and in between two neighbouring neurons. Reassuming, the ZrO 2 :0.5%Tb 7%Y nanoparticles proved to be biocompatible and a valid tool to assess intracellular trafficking dynamics in the neurobiology.

While doping with rare earth ions is used for emission activation, doping with transition metal ions is often used to get specific magnetic properties of a given host material. Recently investigations of transition metal doped materials focused on chances of achieving a room temperature ferromagnetic response. This is because carrier mediated room temperature ferromagnetic order was theoretically predicted for ZnO doped with Mn or Co ions. Such order is required for some of spintronics applications. To realize RT FM both Mn and Co should stay in 2+ charge state, expected when Mn/Co substitute zinc in ZnO. Both ZnMnO and ZnCoO alloys show a strong absorption band, which appears below ZnO band gap transitions. The origin of this absorption in ZnCoO is discussed in the present work. We show based on the results of photoluminescence and photo-ESR investigations that the broad absorption band is related to Co photo-ionization.

Terbium doped yttrium oxide was prepared with the microwave hydrothermal method. The Y 2 O 3 :Tb nanomaterial crystallized as needle-like grains. Bright luminescence in the green region was observed. Significant luminescence intensity increase was obtained after thermal treatment. Reduction of terbium ions was observed after heating in the air atmosphere. Tb 4+ ions were found to be stabilized by crystal impurities. Hydroxyl species were found to have impact on vacancies elimination. The terbium ions were used as optical and magnetic indicator of the material properties.

Although zinc oxide has been widely investigated for many important applications such as laser diodes, photovoltaics, and sensors, some basic properties of this material have not been established up to now. One of these are stopping power values which are crucial for the Rutherford Backscattering Spectrometry analysis. For this kind of measurements, amorphous materials should be used. In this paper we show the results of stopping power measurements for ZnO films grown by Atomic Layer Deposition. The films were grown on a silicon (100) substrate and parameters of the growth were chosen in a way that prevents crystallization of ZnO films. A series of ZnO films with thickness between 20 and 160 nm have been investigated. Extended film characterization has proven that the obtained nanopolycrystalline ZnO films can be considered as truly amorphous with respect to ion beam applications. ZnO films have been used for precise stopping power measurement of MeV He-ions in the energy range from 200 to 5000 keV. These results provide indispensable data for ion beam modification and analysis of ZnO.

The plasmonic photovoltaic effect of mediation by surface plasmons in the harvesting of solar light energy in metallically surface-nanomodified photodiodes or solar cells is described in the microscopic manner. The experimentally observed increase in the efficiency of the photo-effect due to plasmons is explained by the competition between two opposing effects: that of the field concentration in plasmon oscillations and that of the admittance of indirect inter-band transitions in a semiconductor substrate induced by dipole coupling to plasmons at the nanoscale without translational invariance. The former effect favors larger metallic nanocomponents, whereas the latter effect prefers smaller nanocomponents. Both factors are quantitatively addressed within the quantum Fermi golden rule scheme, which allows for the size analysis of the plasmon effect and for its optimization. Experimental verification of the theoretical predictions is presented, including the demonstration of the proximity and size effect in double-layer photo-active substrate. The experiment reveals that the plasmon effect is still present if metallic nanoparticles are separated from substrate by the distance of order of 1 μm.

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].

This work discusses the effect of sample suspension in radio frequency plasma-enhanced chemical vapor deposition process on properties of the obtained overlays. Silicon nitride (SiN x ) overlays were deposited on flat silicon wafers and cylindrical fused silica optical fibers. The influence of the suspension height and fiber diameter on SiN x deposition rate is investigated. It has been found that thickness of the SiN x overlay significantly increases with suspension height, and the deposition rate depends on fiber dimensions. Moreover, the SiN x overlays were also deposited on long-period gratings (LPGs) induced in optical fiber. Measurements of the LPG spectral response combined with its numerical simulations allowed for a discussion on properties of the deposited overlay. The measurements have proven higher overlay deposition rate on the suspended fiber than on flat Si wafer placed on the electrode. Results of this work are essential for precise tuning of the functional properties of new generations of optical devices such as optical sensors, filters and resonators, which typically are based on optical fibers and require the overlays with well defined properties.

This paper is devoted to the development of standard and inverted polymer solar cells based on polyazomethine (PAZ-Car-TPA), poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C 61 butyric acid methyl ester (PCBM). We analyzed the influence of: (i) PEDOT:PSS or MoO 3 as a hole transporting layer in standard devices, (ii) aluminum doping level (from 0 to 3.7%) in ZnO (obtained by atomic layer deposition, ALD) applied as an electron transporting layer in inverted solar cells and (iii) the method applied to obtain ZnO layer (ALD or sol-gel) on its photovoltaic properties. The best device configuration is ITO/AZO (3% Al)/P3HT:PCBM/MoO 3 /Ag which exhibits a power conversion efficiency of 1.51% under about 100 mW/cm 2 AM 1.5 G simulated solar emission. Devices were additionally tested by electrochemical impedance spectroscopy. HOMO-LUMO levels of PAZ-Car-TPA and its mixture with HCl, H 2 SO 4 , p-toluenesulfonic acid, PEDOT:PSS and water were analyzed by cyclic voltammetry and quantum mechanical calculations using Density Functional Theory method.

Iron doped (in the range from 1 to 10 mol %) ZnO nanoparticles (NPs) were obtained by microwave hydrothermal method. The effects of iron content on morphology, crystal structure, optical and magnetic properties of ZnO nanoparticles were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), cathodoluminescence (CL), photoluminescence (PL) and magnetic measurements. XRD studies revealed presence of ZnFe2O4 foreign phase in NPs for iron doping concentrations above 5% placing the solubility limit of Fe in ZnO NPs near this value. The photoluminescence and cathodoluminescence spectra show an increase of the intensity ratio between near band edge (NBE) and deep level emission band (DLE) of ZnO, which is tentatively related by us with intrinsic cracking of ZnO crystals. The blue-shift of NBE band maxima was observed as a concentration of Fe dopant increases. The results of magnetic measurements indicate superparamagnetic behavior of nanoparticles.

In the present work we studied the mechanical properties of hafnium dioxide (HfO2) and aluminium oxide (Al2O3) thin films deposited on glass at low temperature by means of atomic layer deposition method. The scratch resistance and tribological properties of HfO2 and Al2O3 were investigated. During scratch tests the first small cracks in the films were detected with a relatively low load of 3.4–4.9 N. However, up to a load of 30 N, crushing, cracking, and delamination of the Al2O3/glass system not occurs. The tribological experiments revealed a significant difference in the wear between the HfO2 and Al2O3 films. The microcrystalline structure observed for HfO2 resulted in better tribological properties than the Al2O3 film. The addition of a thin zinc oxide interlayer significantly improved the mechanical properties of the system with HfO2 film.

We examine two kinds of volume defects in CdTe-based compounds grown from the melt: cadmium and tellurium inclusions. We have determined their chemical composition by energy-dispersive X-ray spectroscopy and their internal morphology by infrared transmission microscopy. The tellurium inclusions are spheroidal/polyhedral, while the cadmium ones appear star-like. The core size of both the tellurium and the cadmium inclusions is 5–8 μm. Cadmium inclusions cause micro cracks so that they create star-like defects the size of which is about ten times bigger than the inclusions themselves. Each pair of branches in the star-shaped defect we associate with the three easy-cleavage planes (1 1 0) of the zinc blende structure. Using Pockels imaging we have investigated how tellurium and cadmium inclusions influence the electric field distribution in CdTe compounds, which is an important issue for nuclear detectors. Only tellurium inclusions distributed along a continuous plane have an impact on the internal electric field. Neither the separated tellurium inclusions nor the separated cadmium inclusions influence the internal electric field. Crystals of (Cd,Mn)(Te,Se) have a high concentration (104–105 cm−3) of both types of inclusions. In (Cd,Mg)Te there are numerous twin boundaries decorated with tellurium inclusions. Among the studied compounds, (Cd,Mn)Te has the highest quality.

In this paper, cheap and efficient photovoltaic cells based on ZnO/Si heterostructure are discussed. These cells contain zinc oxide nanorods (ZnONR) grown by a low temperature hydrothermal method on a p-type silicon surface. The hydrothermal method applied in the present work uses cheap precursors and allows reproducible and controllable growth of 3D systems. As-grown ZnONR on Si surface are uniformly covered by a zinc oxide (ZnO) layer followed by an aluminum doped zinc oxide (AZO) layer. The latter is deposited on top of the cell as transparent conductive oxide (TCO). Both zinc oxide and aluminum doped zinc oxide layers are grown by a low temperature atomic layer deposition (LT ALD) method. Thickness of ZnO layers is optimized to increase significantly the light-trapping effect and thus the photovoltaic (PV) response. We evaluate impact of ZnO thickness on the PV devices operation. It is found that PV efficiency increases when thickness of the ZnO layer changes from 50 nm to 500 nm. The best response of solar cells is achieved for a sample containing ZnO layer with a thickness equal to 500 nm. The overall photovoltaic response is 10.9% and can be further improved by contact and Si layer optimization.

Lead telluride (PbTe) undoped films with various thicknesses (40–1800 nm) were grown by pulsed laser deposition (PLD) on different single crystal substrates (KCl, Si) and at different substrate temperatures (30 °C, 200 °C). Structural and electrical investigations of the so-obtained films have been carried out. The growth conditions leading to the films having different properties that could be controlled in a possibly wide range were identified. The film crystal structure varied from pseudo-amorphous to a highly ordered one. The films exhibited semiconducting behavior except the case of the thinnest, metallic-like layers. Electrical transport properties of the films with different structural quality were affected by changes of the grain boundary-related potential barrier height whereas donor level-related activation energies remained unchanged.

Dielectric films, such as hafnium dioxide (HfO 2 ), aluminum oxide (Al 2 O 3 ), zirconium dioxide (ZrO 2 ), titanium dioxide (TiO 2 ) and their composite layers are deposited on polycrystalline and amorphous substrates by the atomic layer deposition (ALD) method. We demonstrate that the use of this technology guarantees a uniform and controlled surface coverage in the nanometer scale at low temperatures (in our case, below 100 °C). Modification of the composition of oxide layers allows the deposition of materials with quite different absorption coefficients, refractive indexes and dielectric constants. In particular, we demonstrate structural, electrical and optical properties of dielectric layers and test metal-oxide-semiconductor structures with these oxide materials. Our good quality dielectric layers, obtained at low-temperature ALD, are characterized by a high dielectric constant (above 10), very smooth surface, wide energy gap (above 3 eV), low leakage current (in the range of 10 − 8 A/cm 2 at 1 V), high dielectric strength (even 6 MV/cm) and high refractive indexes (above 1.5 in the visible spectral range).

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.

This work is focused on the electrical and optical analyses used to estimate the activation energy of the dominant shallow donor in thin ZnO films obtained at low temperature by the atomic layer deposition process. These two approaches, based on the temperature-dependent classical Hall effect and photoluminescence investigations, yielded a donor activation energy ED in the range of 30–40 meV, including the estimated error margins. This value, as confirmed by layer composition studies, is attributed to the presence of zinc atoms in the interstitial positions of the ZnO lattice.

In this paper, we report on transparent transistor obtained using laminar structure of two high-k dielectric oxides (hafnium dioxide, HfO 2 and aluminum oxide, Al 2 O 3 ) and zinc oxide (ZnO) layer grown at low temperature (60 °C–100 °C) using Atomic Layer Deposition (ALD) technology. Our research was focused on the optimization of technological parameters for composite layers Al 2 O 3 /HfO 2 /Al 2 O 3 for thin film transistor structures with ZnO as a channel and a gate layer. We elaborate on the ALD growth of these oxides, finding that the 100 nm thick layers of HfO 2 and Al 2 O 3 exhibit fine surface flatness and required amorphous microstructure. Growth parameters are optimized for the monolayer growth mode and maximum smoothness required for gating.

Alcohol vapors sensitivity of a device based on a single mode optical fiber end-face coated with a thin zinc oxide (ZnO) film is presented. The overlays were deposited by Atomic Layer Deposition (ALD) method on both optical fiber tips and silicon reference wafers, and subsequently characterized by means of spectroscopic ellipsometry and scanning electron microscopy. It has been found that the ZnO films show very high quality and they are conformal over the surfaces. The thin ZnO film forms a Fabry-Perot interferometer at the fiber end-face which properties change when the tip is exposed to alcohol vapors. The response of the structure to isopropanol vapors is shown and discussed for different thickness of the ZnO film.

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)

We investigated the aluminum distribution in aluminum-doped zinc oxide films grown by atomic layer deposition. Surface morphology, structure, composition and electrical properties of obtained films were studied. For the aluminum content less than 2 at.%, a periodicity of Al distribution along the layer depth was observed. This periodicity diminished significantly after annealing the samples in nitrogen atmosphere at 300 °C. For the Al content higher than 2 at.%, its distribution in ZnO:Al films was uniform within the depth measurement accuracy of ∼5–10 nm.

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.