Low temperature solution growth is an attractive method for the preparation of nanostructured semiconductor materials with a wide range of applications from optoelectronics to chemical sensing. Despite the widespread application of low temperature solution growth, basic phenomena taking place during the growth are still under debate. The growth is mostly carried out in batch reactors, which are largely scalable and convenient for applied research and industrial applications. The batch reactors are filled with reactants and sealed, and there is no further inflow of the reactants during the growth. As the growth proceeds, the reactants are depleted, and the growth velocities decrease. Conventionally, the growth process is analyzed in static conditions, where the gradual depletion of the reactants in time is neglected. We analyzed time evolution of the growth of ZnO nanorod arrays on conventional sol–gel seed layers and on GaN substrates patterned by focused ion beam lithography. The focused ion beam lithography allows for precise control of the distances between the nanorods in the arrays. We show that for short growth times the growth is reaction limited, while for longer times the growth regime depends on the distance between the nanorods and changes from reaction limited to diffusion limited as the distance between the nanorods decreases. Under diffusion limited growth conditions, the nanorod height depends on the position within the pattern. The nanorods at the edge of the hexagonal pattern with 19 nanorods in diameter are significantly taller than the nanorods in the center. These experimental observations are validated by the solution of the diffusion equation by a finite element method.

No abstract

One dimensional ZnO nanostructures prepared by favorable and simple solution growth methods are at the forefront of this research. Vertically oriented ZnO nanorods with uniform physical properties require high-quality seed layers with a narrow size distribution of the crystallites, strong c-axis orientation, and low surface roughness and porosity. It has been shown that high quality seed layers can be prepared by the sol–gel process. The sol–gel process involves three essential steps: preparation of the sol, its deposition by dip coating, and thermal treatment comprising preheating and annealing. We put emphasis on the investigation of the heat treatment on the properties of the seed layers and on the vertical alignment of the nanorods. It was demonstrated that for the vertical alignment of the nanorods, the preheating step is crucial and that the temperatures reported in the literature have been too low. With higher preheating temperatures, conditions for the vertical alignment of the nanorods were achieved in both investigated annealing atmospheres in air and in argon.

We study the effect of thermal annealing on the electrical properties of the nanoscale p-n heterojunctions based on single n-type ZnO nanorods on p-type GaN substrates. The ZnO nanorods are prepared by chemical bath deposition on both plain GaN substrates and on the substrates locally patterned by focused ion beam lithography. Electrical properties of single nanorod heterojunctions are measured with a nanoprobe in the vacuum chamber of a scanning electron microscope. The focused ion beam lithography provides a uniform nucleation of ZnO, which results in a uniform growth of ZnO nanorods. The specific configuration of the interface between the ZnO nanorods and GaN substrate created by the focused ion beam suppresses the surface leakage current and improves the current-voltage characteristics. Further improvement of the electrical characteristics is achieved by annealing of the structures in nitrogen, which limits the defect-mediated leakage current and increases the carrier injection efficiency.

No abstract

No abstract

No abstract

BackgroundHuntington’s disease (HD) is characterised by involuntary chorea like movements, poor balance, slurred speech, difficulty swallowing, personality change and difficulty thinking manifesting in the middle age of the patients. Changes in behaviour, motor skills and learning correlate with progression of the disease. Thus it is necessary to monitor these changes in new animal models. In 2009, we have generated transgenic minipigs (TgHD) expressing N-terminal (548 aa) part of human huntingtin (Htt) containing 126 CAG/CAA repeats. AimsTo follow disease development in TgHD minipigs of F0, F1 and F3 generation using motoric and behavioural tests. MethodsIn order to follow behavioural and motoric changes we introduced stability pull back test, balance bean, seesaw test, up and down step test, and tunnel test. We also initiated to use accelerometers to monitor walking differences. ResultsWe observed higher fear or inability to perform certain tests, delayed learning period mainly in situations inducing stress in our oldest TgHD animals (F0, F1 generations). The significant difference between WT and TgHD minipigs was noticed in the ability to step on and to cross the elevated balance beam. Pull back stability test showed a significant difference in TgHD animals. Wobbly movements of back legs were observed in the five years old animals. The weight of all the oldest animals dropped in 10% in the last year. ConclusionsThe minipig model starts to show a motoric impairment phenotype, and thus to be a promising model for preclinical testing of new therapeutic approaches of HD. Acknowledgement“The research leading to these results has received funding from the Norwegian Financial Mechanism 2009–2014 and the Ministry of Education, Youth and Sports Project under Contract no. MSMT-28477/2014” (7F14308/2014), and National Sustainability Programme, project number LO1609 (Czech Ministry of Education, Youth and Sports) and RVO: 67985904