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The research has been analyzed by using scanning electron and transmission electron microscopy (SEM and TEM).To research microstructure in single crystal alumina induced by Vickers indentation and the effect of alumina microstructure induced by deformation twinning. Sapphire is a kind of alumina single crystal called Corundum. It has fine machinery, optical, chemistry and anti-radiationary nature and been used widespread in industry world in recent years. Mechanical twinning is the main mode of plastic deformation. It has two types (1) basal twinning (2) rhombohedral twinning. When author pressed 20 N on (0001) plane, it produces B (0001), R1 ( 102) and R1 ¡¨ ( 104) in cross- section. But when pressing 20 N in (1 10) plane, it produces B (0001), B 1 ( 101) and R2 ( 012) in cross-section. In order to understand the role of pressure direction in twinning at room temperature, this research will discuss what effects will be produced twinning microstructure of alumina sample and derivation of dislocation microstructure by using scanning electron and transmission electron microscopy.

Lead halide perovskite solar cells (PSCs) are considered the fastest growing photovoltaic technology, reaching an outstanding certified power conversion efficiency of 24.2% in just 10 years. The best performing PSCs are based on polycrystalline films, where the presence of grain boundaries and ultra-fast crystallization limit the further development of their performance by increasing the bulk and surface defects. Compared to their polycrystalline counterparts, single crystals of lead halide perovskites have been shown to possess much lower trap-state densities and diffusion lengths exceeding 100𝜇m. In this thesis, using a solution space-limited inverse temperature crystallization method, twenty-microns thick single crystals of MAPbI3 are grown directly on the charge selective contact to construct highly reproducible p-i-n inverted type solar cells with fill factors(FF) as high as 84.3% and power conversion efficiencies (PCEs) exceeding 21% under 1 sun illumination (AM 1.5G). A key requisite for high PCEs is avoiding surface hydration, in which moisture attacks the perovskite/transporting layer interface and causes a significant decrease in short-circuit current. These solar cells set a record for single crystal PSCs, and highlight the potential of single crystal PSCs in furthering perovskite photovoltaic technology.

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This dissertation describes experimental studies of the superconducting proximity effect in single-crystal Pb, Sn, and Zn nanowires of lengths up to 60 um, with both ends of the nanowires in contact with macroscopic electrodes that are either superconducting (Sn or Pb) or non-superconducting (Au). The Pb, Sn, and Zn nanowires are fabricated using a template-based electrochemical deposition method. Electric contacts to the nanowires are formed in situ during electrochemical growth. This method produces high transparency contacts between a pair of macroscopic electrodes and a single nanowire, circumventing the formation of oxide or other poorly conducting interface layers. Extensive analyses of the structure and the composition of the nanowire samples are presented to demonstrate that (1) the nanowires are single crystalline and (2) the nanowires are clean without any observable mixing of the materials from the electrodes. The nanowires being investigated are significantly longer than the nanowires with which electrode-induced superconductivity was previously investigated by other groups. We have observed that in relatively short (~6 um) Sn and Zn nanowires, robust superconductivity is induced at the superconducting transition temperatures of the electrodes. When Sn and Pb nanowires are in contact with a pair of Au electrodes, superconductivity is suppressed completely. For nanowires of 60 um in length, although the suppression of superconductivity by Au electrodes is only partial, the induced superconductivity at the higher transition temperatures of the electrodes remains full and robust. Therefore, an anomalous superconducting proximity effect has been observed on a length scale which far exceeds the expected length based on the existing theories of the proximity effect. The measured current-voltage characteristic of the nanowires reveals more details such as hysteresis, multiple Andreev reflection, and phase-slip centers. An interesting relation between the proximity effect and the residual-resistance-ratio of the nanowires has also been observed. Possible mechanisms for this proximity effect are discussed based on these experimental observations.