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We studied degradation mechanisms of ultraviolet InGaN laser diodes emitting in the UVA range. Short wavelength nitride devices are subjected to much faster degradation, under the same packaging and testing conditions, than their longer wavelength counterparts. Transmission electron microscopy analysis of the degraded laser diodes showed pronounced damage to facets in the area of the active layer (waveguide, quantum wells, and electron blocking layer). Energy-dispersive X-ray spectroscopy showed that the active layers were heavily oxidized, forming a compound close in composition to Ga2O3 with proportional addition of Al in the respective area. The oxidation depth was roughly proportional to the intensity of the optical field. We propose UV-light-induced water splitting on a semiconductor surface as a mechanism of the oxidation and degradation of these devices.

We fabricate porous nanostructured 1μm thick ZnO-metal/metal oxide hybrid material thin films using a unique approach utilizing physical vapor deposition with postdeposition annealing. We study Pt, Pd, Ru, Ir and Sn as the metals and find they all form hybrid structures, however with differing physical and electrochemical properties. We investigate their applicability in microsupercapacitor electrodes in a LiCl aqueous electrolyte and find that the ZnO hybrid with Ir exhibits the highest capacitances. We follow with optimization and more detailed material studies of the ZnO-Ir hybrid showing that a significant amount of Ir is present in the material in the form of metallic Ir and indiffused Ir, while IrO2is also present in the nanoscale. We obtain electrodes with 5.25 mF · cm-2capacitance with 90% retention over 10 000 charge/discharge cycles in an aqueous LiCl electrolyte, which is better than the reported values for other Ir-based hybrids. Finally, we showed that the electrodes provide 2.64 mF · cm-2in a symmetric device with an operating voltage of 0.8 V. With this report, we discuss the influence of both Ir and IrO2on the capacitance, underlining the synergistic effect, and show them as promising inorganic matterials for integration with other supercapacitor electrodes.

In this paper, the study of defects in InAs/GaSb type-II superlattices using high-resolution an x-ray diffraction method as well as scanning (SEM) and transmission (TEM) electron microscopy is presented. The investigated superlattices had 200 (#SL200), 300 (#SL300), and 400 (#SL400) periods and were grown using molecular beam epitaxy. The growth conditions differed only in growth temperature, which was 370 °C for #SL400 and #SL200, and 390 °C for #SL300. A wings-like diffuse scattering was observed in reciprocal space maps of symmetrical (004) GaSb reflection. The micrometer-sized defect conglomerates comprised of stacking faults, and linear dislocations were revealed by the analysis of diffuse scattering intensity in combination with SEM and TEM imaging. The following defect-related parameters were obtained: (1) integrated diffuse scattering intensity of 0.1480 for #SL400, 0.1208 for #SL300, and 0.0882 for #SL200; (2) defect size: (2.5–3) μm × (2.5–3) μm –#SL400 and #SL200, (3.2–3.4) μm × (3.7–3.9) μm –#SL300; (3) defect diameter: ~1.84 μm –#SL400, ~2.45 μm –#SL300 and ~2.01 μm –#SL200; (4) defect density: 1.42 × 106 cm−2 –#SL400, 1.01 × 106 cm−2 –#SL300, 0.51 × 106 cm−2 –#SL200; (5) diameter of stacking faults: 0.14 μm and 0.13 μm for #SL400 and #SL200, 0.30 μm for #SL300.

In the present work we analyze the Zn1−xMgxO:Al/Ni/p-GaN system as a transparent electrode for GaN-based UV-LEDs. We first study the properties of the Zn1−xMgxO:Al films obtained by DC magnetron sputtering under various conditions and find that they exhibit anomalous crystallization behavior i.e. not all Mg substituted Zn in the ZnO crystal lattice creating Mg precipitates as well as a lack of correlation between the Mg content and film band gap. Subsequently, we study the behavior of the contact with ultrathin Ni films (2.5–10 nm) introduced at the interface with p-GaN both after deposition as well after annealing steps at temperatures from 400 °C to 750 °C. We use complementary techniques to discuss the structural and chemical properties of the material. We find that the Ni interlayer improved the properties of electrodes, especially their electrical parameters - a 2–3-fold increase in the current at a bias of 2 V was observed. Finally, in a full LED structure, we obtained an enhancement of the 380 nm irradiated power by 9.5% for the Zn1−xMgxO:Al/2.5 nm Ni electrode in comparison with a diode without the Ni interlayer.

The recent rapid development of transparent electronics, notably displays and control circuits, requires the development of highly transparent energy storage devices, such as supercapacitors. The devices reported to date utilize carbon-based electrodes for high performance, however at the cost of their low transparency around 50%, insufficient for real transparent devices. To overcome this obstacle, in this communication highly transparent supercapacitors were fabricated based on ZnO/MnO2 nanostructured electrodes. ZnO served as an intrinsically transparent skeleton for increasing the electrode surface, while MnO2 nanoparticles were applied for high capacitance. Two MnO2 synthesis routes were followed, based on the reaction of KMnO4 with Mn(Ac)2 and PAH, leading to the synthesis of β-MnO2 with minority α-MnO2 nanoparticles and amorphous MnO2 with embedded β-MnO2, respectively. The devices based on such electrodes showed high capacitances of 2.6 mF cm−2 and 1.6 mF cm−2, respectively, at a scan rate of 1 mV s−1 and capacitances of 104 μF cm−2 and 204 μF cm−2 at a very high rate of 1 V s−1, not studied for transparent supercapacitors previously. Additionally, the Mn(Ac)2 devices exhibited very high transparencies of 86% vs. air, far superior to other transparent energy storage devices reported with similar charge storage properties. This high device performance was achieved with a non-acidic LiCl gel electrolyte, reducing corrosion and handling risks associated with conventional highly concentrated acidic electrolytes, enabling applications in safe, wearable, transparent devices.

In the present work we analyze the growth mechanism of Zn/ZnO nanostructured thin films obtained by DC reactive magnetron sputtering with variable absolute gas flow values. Zn target was sputtered at 80 W DC power with variable absolute Ar:O 2 flow values at a set ratio, in sccm: 3:0.3, 6:0.6, 8:0.8, 10:1, 15:1.5, 20:2 and 30:3. We obtained unique Zn/ZnO nanoflowers with morphology and properties changing as a function of gas flow values from dendritic/nanopetal structures for low flow to dense porous films for high flow. Zn core/ZnO shell composition results from surface oxidation of Zn crystallites to 4 nm thick ZnO after exposure to atmospheric air that causes an increase in resistivity especially for denser, more porous films. Taking into account that the plasma properties measures using the Langmuir probe and optical emission spectroscopy remain constant as a function of gas flow values, we put forward that the structural evolution of films is influenced by oxygen incorporating into the film surface acting as an inhibitor − incorporating into the films and decreasing crystallite sizes and amorphizing the film structure.

Detailed microstructural studies were performed on Ni/Si ohmic contacts to silicon carbide in order to investigate the effect of initial Ni:Si ratio in as-deposited structures on the occurrence of characteristic defects in Ni silicide layers, such as voids, layer discontinuities, rough surface or rough interface. The chosen range of investigated Ni:Si ratios corresponded to δ-Ni 2 Si as a dominant phase after complete annealing sequence. Strong effect of the initial stoichiometry on the ohmic contact's microstructure was observed. The highest Ni concentration significantly lowered the temperature at which roughening of the surface and the interface occurred. The middle value of investigated concentrations resulted in the rough interface after high temperature annealing, while the lowest investigated Ni content preserved smooth interface but introduced large voids and layer discontinuities. After the first annealing step, γ-Ni 31 Si 12 and/or δ-Ni 2 Si phases were detected. In the ohmic contacts (after two-step annealing sequence), beside δ-Ni 2 Si, the metastable, high temperature phase θ-Ni 2 Si was detected (also referred to as Ni 3 Si 2 ·h). This phase can exist within a relatively broad range of Ni:Si stoichiometry. The stoichiometry change toward higher Si content, which occurs during high temperature annealing, was realized through this phase. Superstructures were detected in θ-Ni 2 Si (Ni 3 Si 2 ·h) and in γ-Ni 31 Si 12 grains. The effect of the stoichiometry change on the morphology of the Ni silicide layers is discussed.

This report presents the results of fabricating GaN nanorods by inductively coupled plasma etching using BCl 3/Cl 2 chemistry. Interestingly, the GaN nanorods are formed only in the area initially masked by the sacrificial metal mask. In addition to the metallic mask, a specific feature of this process is the application of an insulating ceramic carrier for the improvement of the process performance. The authors show that using the same etching parameters but with a conductive silicon carrier significantly reduces the efficiency of nanorod formation. Auger electron spectroscopy was applied to propose and confirm the mechanism of nanorod formation ceramic carrier and properly selected metallic masks. The usefulness of the developed method of nanorod production has been confirmed by its application in the fabrication and characterization of GaN-based UV light-emitting diodes.

Effects of aluminum (Al) and nitrogen (N) implantation performed at room and at elevated (500 °C) temperatures on epitaxial n-type 4H polytype silicon carbide as well as post-implantation annealing have been studied by Raman scattering spectroscopy. The amorphization of 4H–SiC is observed because of ion implantation effects. The Raman analysis showed that the recovery of the crystallinity increased with an increase in the annealing temperature. However, for samples implanted with high doses, the full crystal recovery was not complete even with annealing temperatures up to 1800 °C, and crystal defects were still present in the recrystallized layer, which was confirmed by transmission electron microscopy. Raman scattering spectra were collected at room temperature using a micro-Raman spectrometer. The visible (488 nm) and deep ultraviolet (266 nm) lasers were used as excitation sources. For the DUV laser, the optical penetration depth is less than the implanted layer thickness, and the area near the surface layer can be exactly probed. In contrast, the visible Raman spectrum shows bands characteristic of bulk 4H–SiC, which arise from the underlying non-implanted region. Based on the analysis of the longitudinal optical phonon–plasmon coupled mode, the electrical parameters for N2+ implanted samples were evaluated, where electron concentration n = 3.05 × 1018 cm−3 and mobility μ = 50 cm2/V s, respectively. The results are consistent with the parameters measured by the Hall method.

Dye sensitized solar cells were fabricated using ZnO nanostructured photoelectrodes sensitized with N-719 or Rose Bengal dyes. We assessed the device performance as a function of the sensitization time and found a dependence on time for the N-719 and no significant changes for the Rose Bengal. Furthermore, we observe that the structure of the N-719 molecule beneficial for sensitization of TiO2 may lead to the degradation of the ZnO crystals and a growth of an amorphous shell limiting dye performance in the cells.

We demonstrate nanocrystalline ZnMgO:Al transparent conducting films grown by room temperature magnetron sputtering. Unlike in the usual ZnMgO films grown by sputtering, the crystal orientation perpendicular to the substrate surface is strongly disrupted with the addition of Mg, even well below the phase separation threshold of Mg/(Mg + Zn) = 0.43. We argue that the presence of Al in the films promotes disoriented growth. Using transmission, Rutherford Backscattering Spectroscopy and electron microscopy measurements, we prove that not all Mg in the films substitutes Zn in the ZnO lattice, but also forms of precipitates. We apply the highest transmission films as contact electrodes to the p-GaN layer in a GaN-based 385 nm UV LED structure. By replacing the common opaque Ni/Au ohmic contact to p-GaN in ring geometry by a circular ZnMgO:Al electrode we obtain a 250% increase in irradiated power, which is also 148% higher than when Ni/Al is replaced by ZnO:Al.

The new approach to fabrication process of nickel-based ohmic contacts to silicon carbide (SiC) is presented. During the first annealing step (300 °C), the amorphous Ni–Zr layer retards diffusion between two nickel silicide layers, thus handling the contradictory requirements for optimal Ni:Si ratio. Different stoichiometry obtained in each silicide layer allows to preserve smooth interface with SiC and simultaneously to avoid relatively easily meltable Si-rich Ni–Si phases during high temperature annealing (1000 °C) and therefore prevents morphology degradation. After annealing at 1000 °C only one final nickel silicide layer is present and Zr atoms are agglomerated at its surface. Morphology of the final silicide layer is substantially improved when compared to typical Ni-based contacts obtained by similar high-temperature annealings. The improved microstructure of the ohmic contact is a promising advantage in terms of SiC devices reliability.

Display Omitted Three types of GaN: MOVPE-grown, MBE-grown, ammonothermal-grown were used in the experiment.Master stamp used in the experiment consisted of glass covered with metallic layer.The pattern of the master stamp was fabricated by FIB.Soft stamps were replicated from master stamps.Triple mask was used for imprinted pattern transfer into GaN. In this paper results on GaN patterning using nanoimprint technology are presented. Direct method of stamp fabrication based on FIB etching was used. Stamp with critical dimensions of 50nm was achieved. Two kinds of polymer materials were used for master stamp replication. Influence of etching parameters using chlorine based plasma on GaN etch rate and surface roughness was discussed. Triple mask consisting of TU2 resist, Cr and SiO2 used for NIL-generated pattern transfer into GaN allowed successful patterning.

Conditions of fabrication of first order distributed-feedback surface gratings designed for single-mode Al 0.45 Ga 0.55 As/GaAs quantum cascades lasers with the emission wavelength of about 10μm are presented. The 1 μm-deep rectangular-shaped gratings with the period of about 1.55 μm and duty cycle in the range of 65-71% made by the standard photolithography are demonstrated. The wavenumber difference of about 7 cm -1 at 77 K is observed for the radiation emitted by lasers fabricated from the same epitaxial structure with ridge widths in the range of 15-25 μm. Moreover, the emission wavelength of the lasers could be tuned with temperature at a rate of 1 nm/K in the temperature range of 77-120 K. The full width at half maximum of the emitted spectra is ~ 0.4 cm -1 .

Photoluminescence studies of nanocoral ZnO nanostructures, fabricated using magnetron sputter deposition of porous Zn films with subsequent oxidation by RTP annealing at 400–800 °C is presented. Structural characterization of the films performed using electron microscopy techniques show the nanocoral morphology of the films with individual coral branches constituting of bunched single crystal ZnO grains of 30–100 nm in dimensions. High resolution images confirm the high quality of individual grains. The features in the photoluminescence spectra are identified using temperature-dependent and power-dependent measurements, with rich features observed in the excitonic region at 5 K, as well as zinc vacancy lines and surface-state recombination lines being present. It is found, that the spectra significantly depend on the annealing temperatures of the samples, with the spectra acquired for the sample annealed at 800 °C exhibiting stronger excitonic emission by 2 orders of magnitude than any other features, thus proving the highest structural quality of the nanostructures.

Distribution of chemical composition in nickel-based ohmic contacts ton-type 4H-SiC was investigated with XEDS mapping performed on plan-view and cross-sectional TEM samples. Obtained results indicate that local deviations in stoichiometry from that of Ni2Si phase significantly contribute to degradation of surface morphology.

Nanocoral ZnO structures are fabricated by means of reactive magnetron sputtering with post deposition annealing. The films are polycrystalline with highly developed surfaces. Their application for biosensing is presented in the extended-gate FET approach where a nanocoral gate electrode is used to sense the pH of the solution and then the presence of BSA molecules.

In this work the electrical properties of Ni and Ni2Si contacts on n-type 4H-SiC were correlated to the strong structural changes at the contact/SiC interface upon annealing. We can conclude that only δ-Ni2Si grains play a main role in determining electrical transport properties of the Ni-based ohmic contacts to n-SiC. It is presumed that a recrystallization and texturization of δ-Ni2Si phase on (0001)SiC-surface during high temperature annealing (> 900°C) contributes to the change of barrier heights, as well as specific contact resistance of contacts.

Ni/Si multilayer contact structures to 4H-SiC after subsequent annealing steps are investigated with electron microscopy methods. After high temperature annealing step, specific defects in the contact structures are observed. The influence of phase transformations during annealings on the morphology on the contacts is discussed and the explanation of formation mechanism of voids within contact layer is proposed.

AIXTRON SE, Kaiserstr. 98, 52134 Herzogenrath, Germany Received 17 October 2011, revised 22 November 2011, accepted 25 November 2011 Published online 16 December 2011 Key words wide bandgap semiconductors, SiC, GaN, ohmic contacts, diffusion barriers. Presented are the theoretical and experimental fundamentals of the fabrication of ohmic contacts to n- and p-type wide band gap semiconductors such as SiC and GaN. In particular, the Ni-Si/n-SiC, Al-Ti/p-SiC, Ti-Al/n-GaN and Ni-Au/p-GaN systems are discussed with the focus on the thermally activated chemical reactions taking place at the metal-semiconductor interface, that lead to the appearance of ohmic behaviour in the contact. Examples of reactions at very intimate interfaces are shown, which are irresolvable using even such sophisticated characterisation methods as high-resolution transmission electron microscopy and can only be explained using modelling. The issue of thermal stability of the contacts is discussed and the introduction of specifically designed diffusion barriers (eg. Ta-Si-N) into the contact metallisation stack is presented as a solution improving drastically the thermal stability of the contacts without degrading their electrical properties.

Nickel silicide ohmic contacts to 4H n-SiC were investigated using electron microscopy. Ni/Si multilayer structures were fabricated using magnetron sputtering technique. The Ni to Si layer thickness ratio was chosen to achieve the stoichiometry of Ni2Si phase. The deposited structure was subjected to a two-step annealing procedure. First annealing step was performed at 600C, the second at 1050C or 1100C. Microstructure and morphology after each annealing step were characterized using scanning and transmission electron microscopy. The specific voids and discontinuities of the layer were observed after annealing at high temperature. Phase compositions were investigated with electron diffraction technique. After annealing at 600C the phases Ni2Si, Ni3Si2 and Ni31Si12 were detected. High temperature annealing resulted in the presence of only Ni2Si phase. The influence of phase transformations on the morphology of the contacts is discussed. Explanation of the origin of layer discontinuities is proposed. [doi:10.2320/matertrans.MB201014]

AlGaN/GaN high electron mobility transistors on semi-insulating bulk ammonothermal GaN have been investigated. By application of regrown ohmic contacts, the problem with obtaining low resistance ohmic contacts to low-dislocation high electron mobility transistor (HEMT) structures was solved. The maximum output current was about 1 A/mm and contact resistances was in the range of 0.3&ndash, 0.6 &Omega, &middot, mm. Good microwave performance was obtained due to the absence of parasitic elements such as high access resistance.

The stability of Au wire connections to n-SiC/Ti ohmic contacts and to n-SiC/Ni ohmic contacts with top Au or Pt layers has been investigated. Long-term tests of the connections are performed in air at 400oC. Evaluation of electrical parameters, morphology and structure of the metallization as well as the strength of Au joint show stable Au wire bonds to the metallization with Ti-ohmic contacts.

The reliability of Ni2Si/n-SiC ohmic contacts with Au overlayer either without or with Ta-Si-N diffusion barrier was investigated after long-time aging in air at 400oC and rapid thermal annealing in Ar up to 800oC. It is shown that aging of the Au/Ni2Si/n-SiC contacts in air at 400oC resulted in complete degradation due to both oxygen penetration and interdiffusion/reaction processes. In contrast, only a small change in properties was detected on the contacts annealed in Ar at 800°C. The stability of both electrical and structural properties of Au/TaSiN/Ni2Si/n-SiC thermally stressed contacts at different conditions points out their superior thermal stability.

With the development of novel device applications, e.g. in the field of robust and recyclable paper electronics, came an increased demand for the understanding and control of IGZO Schottky contact properties. In this work, a fabrication and characterization of flexible Ru–Si–O/IGZO Schottky barriers on paper is presented. It is found that an oxygen-rich atomic composition and microstructure of Ru–Si–O containing randomly oriented Ru inclusions with diameter of 3–5 nm embedded in an amorphous SiO2 matrix are effective in preventing interfacial reactions in the contact region, allowing to avoid pre-treatment of the semiconductor surface and fabricate reliable diodes at room temperature characterized by Schottky barrier height and ideality factor equal 0.79 eV and 2.13, respectively.

The thermal degradation of Au/Ni2Si/n-SiC ohmic contact was investigated after long-time aging in air at 400 °C or rapid thermal annealing in Ar up to 700 °C. Current–voltage characteristics, sheet resistance measurements, Rutherford backscattering spectrometry, X-ray diffraction and scanning electron microscopy were used to characterize the contacts before and after heat treatments. Thermal stress at different conditions shows different influence on the properties degradation of Au/Ni2Si/n-SiC ohmic contacts. It is shown that aging of the contacts in air at 400 °C resulted in complete degradation due to both oxygen penetration and inter-diffusion/reaction processes at the metal/SiC interface. In contrast, only a small change in contact morphology was detected on the contacts annealed in Ar at 700 °C.

The thermal stability of Ni"2Si/n-SiC ohmic contacts with Au overlayer without or with Ta-Si-N diffusion barrier was investigated after long anneals at 400^oC in air. Current-voltage characteristics, sheet resistance measurements, Rutherford backscattering spectrometry, X-ray diffraction and scanning electron microscopy were used to characterize the contacts before and after aging. It is shown that aging of Au/Ni"2Si/n-SiC contact at 400^oC for 50h resulted in electrical failure, as well as complete contact degradation for 150h due to interdiffusion/reaction processes in the contact. The Au/Ta"3"5Si"1"5N"5"0/Ni"2Si/n-SiC contact is thermally stable after 150h of aging at 400^oC and has great potential for use in SiC-based devices for high-temperature operation.

GaN nanorods have been formed by inductive coupled plasma (ICP) etching in BCl3/Cl2 plasma. Nanostructures were formed only in the initially titanium masked area, wherein the dimensions of mask pattern do not define dimensions of nanorods, but the region of structure formation only. It has been found that density of nanorods strongly depends on process parameters, such as RF and ICP power, and gas pressure. Possible mechanisms of nanorods formation have been suggested, without however decisive conclusion.

The effect of high temperature (HT, up to 1400 K)–hydrostatic pressure (HP, up to 1.2 GPa) on Czochralski silicon implanted with hydrogen (Si:H, H dose, D H = 5 × 1 0 16 cm − 2 ), helium (Si:He, D He = 5 × 1 0 16 cm − 2 ) or helium + hydrogen (Si:He, H, total D H + He = 1 × 1 0 17 cm − 2 ) has been investigated by TEM, SIMS and PL measurements. The treatment of Si:H, Si:He and Si:He, H at ≤1070 K–HP results in a formation of buried nanostructured layers composed of hydrogen/helium filled cavities/platelets and numerous point and extended defects; much fewer dislocations are created at ≥1270 K–HP. The microstructure of Si:He, H evidences specific interaction of implanted helium and hydrogen, affecting the creation of Si–H bonds.

Catalyst-free growth of ZnO nanowires using reactive magnetron sputtering at room temperature is reported. We discuss the growth of the nanowires using reactive magnetron sputtering as a function of argon and oxygen flow values changing at a set ratio of 10:2. A transition from nanostructured Zn to nanowire ZnO growth is observed at 20 sccm Ar and 4 sccm O2. Densification and improved alignment of the nanowires is visible for increasing flow values up to 50 sccm Ar and 10 sccm O2. Nanowires exhibit stacking fault regions of zinc blende ZnO in wurtzite ZnO. The regions encompass the whole width of the nanowires and their quantum well behavior is manifested in the photoluminescence spectra. The nanowires were subsequently deposited on paper and PET substrates and electromechanical nanogenerators were fabricated. Manual pressing and depressing of the devices induced voltages of 50 μV and 2 μV for the devices on PET and paper substrates, respectively.

Nickel-based contacts with additional interfacial layer of carbon, deposited on n-type 4H-SiC, were annealed at temperatures ranging from 600 to 1000°C and the evolution of the electrical and structural properties were analyzed by I-V measurements, SIMS, TEM, and Raman spectroscopy. Ohmic contact is formed after annealing at 800°C and minimal specific contact resistance of about 2.0×10-4 Ω cm2 has been achieved after annealing at 1000°C. The interfacial carbon is amorphous in as-deposited state and rapidly diffuses and dissolves in nickel forming graphitized carbon. This process activates interfacial reaction between Ni and SiC at lower temperature than usual and causes the formation of ohmic contact at relatively low temperature. However, our results show that the specific contact resistance as well as interface quality of contacts was not improved, if additional layer of carbon is placed between Ni and SiC.

Titanium-aluminum alloys were successfully used to form low resistance ohmic contacts to p-type SiC. This work concerns two Al-Ti alloy compositions. Contacts were prepared by magnetron sputtering of bilayer Al-Ti and trilayer Ti-Al-Ti thin films and rapid thermal annealing at temperatures range 900°C ÷ 1000°C. Using scanning electron microscopy and profiler, an investigation of surface morphology of annealed contacts was conducted. The best resistivity of 5.8·10−5 Ωcm2 was attained on 100nm/26nm Al/Ti metallization of 80% at. Al alloy composition annealed at 1000°C for 2 min. Relatively low roughness of 30 nm was observed on trilayer Ti/Al/Ti metallization.

Single orientation ZnO (00.2) films were deposited by means of high temperature high vacuum reactive magnetron sputtering onto Al2O3 (0001) and GaN (0001) substrates. In order to obtain films of high crystalline quality a novel approach to ZnO sputter deposition was employed, adapting the practice used in MBE technology, of using a MgO buffer layer deposited on sapphire at a high-temperature followed by a ZnO nucleation layer deposited at low temperature. ZnO films were also grown on epitaxial GaN/Al2O3 substrates where the GaN layer was treated as the buffer layer. Following the deposition, all samples were annealed ex-situ in an O2 flow at 800°C. The obtained ZnO films have a lattice constant c equal to 5.2036 Å and 5.214 Å for the films deposited on Al2O3 and GaN substrates, respectively. Secondary ion mass spectroscopy depth profiles, scanning and transmission electron microscopy cross sectional images and atomic force microscope were used to characterize the structural properties of the films. Electrical properties were assessed using Hall effect measurement. Photoluminescence spectra were also taken.

This study focuses on the relationships between the process parameters during magnetron sputter deposition of MnO2 and the resulting film properties. Three MnO2 phases were identified - γ, β and λ and the dependence of MnO2 phase presence on the oxygen content in the sputtering atmosphere was found. Selected MnO2 phases were subsequently applied as ultrathin coatings on top of nanostructured ZnO electrodes for transparent supercapacitors with LiCl-based gel electrolyte. The films containing λ-MnO2 exhibited both the highest optical transparency of 62% at 550 nm as well as the highest specific capacitance in the supercapacitor structure, equal to 73.1 μF/cm2. Initially lower, the capacitance was elevated by charge-discharge conditioning.

In the paper, the results of technological investigations on planar optical waveguides based on high band gap oxide semiconductors were presented. Investigations concerned the technologies of depositing very thin layers of: zinc oxide ZnO, titanium dioxide TiO2 and tin dioxide SnO2 on substrates of quartz glass plates. There were investigated both morphological structures of the produced layers and their optical properties. The paper also presents investigations on the technology of input-output light systems in the Bragg grating structures.