Single crystal

About: Single crystal is a research topic. Over the lifetime, 59617 publications have been published within this topic receiving 870828 citations.

Formation and Properties of Porous Silicon and Its Application

Abstract: Preparation, properties, and applications of porous silicon film were investigated. Silicon single crystal is converted into porous silicon film by anodization in concentrated hydrofluoric acid at currents below the critical current density. When an n‐type silicon was anodized, the silicon surface was illuminated to generate holes which were necessary for this anodic reaction. The growth rate of the film, from n‐type silicon, was larger than that from p‐type silicon in this experimental condition. The crystalline structure was the same as that of silicon single crystal. A new isolation technique for bipolar integrated circuits was proposed by making use of the properties of the film such that it can be formed several microns thick and oxidized easily to form an insulator. The main feature of the technique is that it provides a means to form thick insulating film inlaid through the n‐type epitaxial layer without prolonged heat‐treatment. A preliminary experiment was carried out to test the practical usage of the technique.

Atomic Binding of Transition Metals on Clean Single‐Crystal Tungsten Surfaces

Abstract: The binding energy of single atoms of the Period‐6 transition elements on atomically perfect single‐crystal planes of tungsten was measured by utilizing low‐temperature‐pulse field desorption, in a ultrahighvacuum field‐ion microscope. For any given adatom, the dependence of the binding energy on surface crystallography was observed to be inconsistent with a pairwise interaction model. A new model incorporating a surface‐charge redistribution into a pairwise potential is shown to be consistent with the data. The variation in binding energy with electronic configuration of the adatom is interpreted in terms of an electron‐energy band model. The binding energy depends upon the electron occupancy of two subbands assumed to exist in the d levels of the atom, when it is adsorbed on the surface. Finally, the abnormal field‐desorption properties of adatoms on the (110) plane are discussed in terms of its anomalous work function.

Oxide ionic conductivity of apatite type Nd9·33(SiO4)6O2 single crystal

Abstract: Single crystal of hexagonal apatite type Nd 9·33 (SiO 4 ) 6 O 2 which is an oxide ionic conductor was prepared by the FZ method and an anisotropy of its conductivity was investigated. The conductivity of a parallel component to a c-axis (2·1×10 −8 S cm −1 at 30°C) was higher about one order of magnitude, compared with that of perpendicular component.

Real-Space Imaging of the Atomic Structure of Organic-Inorganic Perovskite.

Abstract: Organic-inorganic perovskite is a promising class of materials for photovoltaic applications and light emitting diodes. However, so far commercialization is still impeded by several drawbacks. Atomic-scale effects have been suggested to be possible causes, but an unequivocal experimental view at the atomic level is missing. Here, we present a low-temperature scanning tunneling microscopy study of single crystal methylammonium lead bromide CH3NH3PbBr3. Topographic images of the in situ cleaved perovskite surface reveal the real-space atomic structure. Compared to the bulk we observe modified arrangements of atoms and molecules on the surface. With the support of density functional theory we explain these by surface reconstruction and a substantial interplay of the orientation of the polar organic cations (CH3NH3)(+) with the position of the hosting anions. This leads to structurally and electronically distinct domains with ferroelectric and antiferroelectric character. We further demonstrate local probing of defects, which may also impact device performance.

Unraveling the Exciton Binding Energy and the Dielectric Constant in Single-Crystal Methylammonium Lead Triiodide Perovskite.

Abstract: We have accurately determined the exciton binding energy and reduced mass of single crystals of methylammonium lead triiodide using magneto-reflectivity at very high magnetic fields. The single crystal has excellent optical properties with a narrow line width of ∼3 meV for the excitonic transitions and a 2s transition that is clearly visible even at zero magnetic field. The exciton binding energy of 16 ± 2 meV in the low-temperature orthorhombic phase is almost identical to the value found in polycrystalline samples, crucially ruling out any possibility that the exciton binding energy depends on the grain size. In the room-temperature tetragonal phase, an upper limit for the exciton binding energy of 12 ± 4 meV is estimated from the evolution of 1s–2s splitting at high magnetic field.