915 research outputs found
Study of the self-organization of atoms and molecules on the surface of silicon and germanium by means of scanning tunneling microscopy
Среди различных подходов последние годы все большее внимание исследователей привлекает создания наноструктур из отдельных атомов и молекул (так называемая технология «снизу вверх») с использованием механизмов самоорганизации. В докладе будут представлены возможности сканирующей туннельной микроскопии для исследования топографии поверхности, ее состава, атомной и локальной электронной структуры. При этом основное внимание будет уделено количественным аспектам методов и точности измерений.Among the various approaches in recent years, much attention of researchers has been attracted to the creation of nanostructures from individual atoms and molecules (the so-called bottom-up technology) using self-organization mechanisms. The report will present the possibilities of scanning tunneling microscopy for studying the topography of a surface, its composition, atomic and local electronic structure. The main attention will be paid to the quantitative aspects of the methods and accuracy of measurements
Self-assembled quasi-1D and 2D nanostructures of fullerenes on silicon
The work was supported by Russian Foundation for Basic Researches (Grant No. 17-02-00577)
Metal-insulator transition in the In/Si(111) surface
The metal-insulator transition observed in the In/Si(111)-4x1 reconstruction
is studied by means of ab initio calculations of a simplified model of the
surface. Different surface bands are identified and classified according to
their origin and their response to several structural distortions. We support
the, recently proposed [New J. of Phys. 7 (2005) 100], combination of a shear
and a Peierls distortions as the origin of the metal-insulator transition. Our
results also seem to favor an electronic driving force for the transition.Comment: Presented in the 23 European Conference in Surface Science, Berlin,
September 2005. Submitted to Surface Science (proceedings of the conference)
in August 200
Ion Dynamics in Single and Multi-Cation Perovskite
In organic-inorganic perovskites currently widely used to fabricate high-efficiency solar cells the electrical properties are to a large extent determined by the presence of mobile ions. These mobile ions are commonly held responsible for many undesirable features of perovskite solar cells, such as hysteretic behavior of electrical properties and degradation of parameters during operation. Hence, developing methods to study the properties of mobile ions and distinguish their contribution to electrical properties from the usual effects due to electronic states are essential for gaining control over the type and density of mobile ions. In this paper we show that comparison of deep levels transient spectroscopy (DLTS) measurements performed in the normal and reverse biasing/pulsing sequences provides a useful means of discriminating between the contributions of electronic traps usual for all semiconductors and the mobile ions very important in perovskites. To simplify things these experiments were performed on Schottky diodes rather than heterojunctions with organic-inorganic electron transport and hole transport layers. The results of experiments are presented and compared for single cation MAPbI(3)and multication perovskites. In both cases the main features observed in DLTS could be attributed to mobile ions
(Tl, Au)/Si(111) and (Tl, Au)/Si(100) 2D compounds: Atomic and electronic structure and transport properties
Electronic band structure of a Tl/Sn atomic sandwich on Si(111)
A two-dimensional compound made of one monolayer of Tl and one monolayer of Sn on Si(111) has been found to have a sandwichlike structure in which the Sn layer (having the milk-stool arrangement) resides on the bulklike terminated Si(111) surface and the Tl layer (having the honeycomb-chained-trimer arrangement) is located above the Sn layer. The electronic band structure of the compound contains two spin-split surface-state bands, of which one is nonmetallic and the other is metallic. Near the Fermi level the metallic band is split with the momentum splitting Δk∥=0.037 Å−1 and energy splitting ΔEF=167 meV. The steep dispersion of the band when crossing the Fermi level corresponds to an electron velocity of ≈8.5×105 m/s, which is comparable to the value reported for graphene. The 2D Fermi contours have almost circular shape with spin texture typical for hexagonal surfaces
Ion-beam sputtering of NiO hole transporting layers for p-i-n halide perovskite solar cells
Ion-beam sputtering offers significant benefits in terms of deposition
uniformity and pinhole-free thin-films without limiting the scalability of the
process. In this work, the reactive ion-beam sputtering of nickel oxide has
been developed for the hole transporting layer of a p-i-n perovskite solar
cells (PCSs). The process is carried out by oxidation of the scattered Ni
particles with additional post-treatment annealing regimes. Using deposition
rate of 1.2 nm/min allowed growth of very uniform NiO coating with the
roughness below 0.5 nm on polished Si wafer (15x15 cm2). We performed a complex
investigation of structural, optical, surface and electrical properties of the
NiO thin-films. The post-treatment annealing (150-300C) was considered as an
essential process for improvement of the optical transparency, decrease of
defects concentration and gain of the charge carrier mobility. As result, the
annealed ion-beam sputtered NiO films delivered a power conversion efficiency
(PCE) up to 20.14%, while device without post-treatment reached the value of
11.84%. The improvement of the output performance originated from an increase
of the short-circuit current density (Jsc), open circuit voltage (Voc), shunt
and contact properties in the devices. We also demonstrate that the ion-beam
sputtering of NiO can be successfully implemented for the fabrication of large
area modules (54.5 cm2) and PSCs on a flexible plastic substrate (125 microns)
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