Fabricating perovskite single-crystal thin films (SCTFs) in controllable manner is the major challenge for the promising potential applications in optoelectronic devices. Although modifying the substrate surface is frequently used to realize the controlled growth of perovskite SCTFs, it is still unclear how the substrate condition affects the crystallization process. In this work, we systemically investigated the effects of the surface hydrophobicity of indium tin oxide substrates on the crystallization process of MAPbBr 3 SCTFs prepared by the space-confined method. Comprehensive characterizations show that the surface morphology and crystallinity of SCTFs are improved, and the defect density is reduced when increasing the substrate hydrophobicity. The best MAPbBr 3 thin film obtained has a full width at half-height of the rocking curve of the (001) crystal plane of 0.044°. The mechanism of the substrate hydrophobicity on the crystal growth is also discussed. These results will provide guidance to the controllable growth of high-quality SCTFs for perovskite SCTF devices.

Differential cross sections for evaporation residues and fission fragments for 35A, 100A, 130A and 155A MeV 14 N on targets ranging from 154 Sm to 197 Au have been measured. The angle-integrated cross sections are larger than what might be expected. The fission fragment-fission fragment folding angle correlations for 35A, 100A MeV 14 N and 25A MeV 16 O on similar targets were also measured. The average linear momentum transfer has been deduced from both the fission angle correlation and from the fore-aft asymmetry of the fission angular distributions in the laboratory system. The data are all consistent with a picture where pre-equilibrium particle emission removes an increasing fraction of the orbital angular momentum as the bombarding energy increases. This allows a large range of partial waves to contribute to formation of a composite nucleus with a finite fission barrier.PACS number͑s͒: 25.70.Jj

Characteristics of hot electrons produced in the interaction of femtosecond laser pulses with foil targets were investigated at a moderate laser intensity. Both outgoing and ingoing hot electrons from the femtosecond laser plasma were studied. A collimated jet of outgoing hot electrons was observed in the target normal direction. An ingoing energetic hot-electron beam was found in the laser propagation direction, while the low-energy ingoing electrons spread into wider cone angle due to the collisional effects in the plasma and target material. These observations were supported by three-dimensional Monte Carlo simulations. The hot-electron temperature obtained from electron spectra and absorption experiments implies that resonance absorption is partially responsible for the generation of hot electrons.

The crystal quality limits the mobility-lifetime (μτ) product and the further applications of perovskite single crystals (PSC) in high energy radiation detections regardless of their high attenuation coefficient. In this paper, high-quality and controllable growth of MAPbX3 PSCs is demonstrated using the liquid-diffusion induced crystallization (LDSC) method. The growth kinetics are modeled to demonstrate the feasibility of the controllable growth via keeping the growth in the mass-transport-limited regime. The crystal growth rate is confirmed theoretically and experimentally to be constant and solely dependent on the growth temperature. A facile method is developed to measure the growth rate without disturbing or suspending the whole process. MAPbBr3 PSC grown at the optimal condition demonstrates a full-width at half-maximum of the (100) X-ray rocking curves of 0.0096°, a fluorescence lifetime of 1099 ns, a trap density of 4.5 × 109 cm–3, and a μτ product of 1.495 × 10–2 cm2 V–1. The resulting MAPbBr3 X-ray detector has a sensitivity of 2181 μC Gyair –1 cm–2. All results indicate that the controllable growth is beneficial to the crystal qualities and device performances. The concept proposed here will be inspiring for the community of researchers of perovskite materials.

The impact parameter dependence of light charged particle ( p,d,t,␣) emission has been studied using an impact parameter selection based on coincident detection of residues or fission fragments. The energy spectra at twelve angles between 20°and 150°have been fit by a multiple moving source parametrization. The angle and energy integrated preequilibrium proton multiplicities decrease with increasing impact parameter in qualitative agreement with a Fermi jet calculation. The preequilibrium d/ p and t/ p multiplicities increase slowly with increasing impact parameter and are nearly identical at the two bombarding energies. The preequilibrium ␣/p ratio shows a less consistent dependency on impact parameter but decreases significantly with increasing bombardment energy. A calculation of the d/p and t/ p multiplicity ratios with a transport model incorporating complex particle emission is quite successful in reproducing the absolute magnitude, impact parameter dependence, and bombarding energy dependence of the experimental total multiplicities.