High-resolution investigations of ripple structures formed by femtosecond laser irradiation of silicon

We report on the structural investigation of self-organized periodic microstructures (ripples) generated in Si(100) targets after multishot irradiation by approximately 100-fs to 800-nm laser pulses at intensities near the single shot ablation threshold. Inspection by surface sensitive microscopy, e.g., atomic force microscopy (AFM) or scanning electron microscopy (SEM), and conventional and high-resolution transmission electron microscopy reveal complex structural modifications upon interaction with the laser: even well outside the ablated area, the target surface exhibits fine ripple-like undulations, consisting of alternating crystalline and amorphous silicon. Inside the heavily modified area, amorphous silicon is found only in the valleys but not on the crests which, instead, consist of highly distorted crystalline phases, rich in defects

On the electronic properties of a single dislocation

A detailed knowledge of the electronic properties of individual dislocations is necessary for next generation nanodevices. Dislocations are fundamental crystal defects controlling the growth of different nanostructures (nanowires) or appear during device processing. We present a method to record electric properties of single dislocations in thin silicon layers. Results of measurements on single screw dislocations are shown for the first time. Assuming a cross-section area of the dislocation core of about 1 nm2, the current density through a single dislocation is J = 3.8 × 1012 A/cm2 corresponding to a resistivity of ρ ≅ 1 × 10-8 Ω cm. This is about eight orders of magnitude lower than the surrounding silicon matrix. The reason of the supermetallic behavior is the high strain in the cores of the dissociated dislocations modifying the local band structure resulting in high conductive carrier channels along defect cores

Structural and electronic properties of epitaxial multilayer h-BN on Ni(111) for spintronics applications

Hexagonal boron nitride (h-BN) is a promising material for implementation in spintronics due to a large band gap, low spin-orbit coupling, and a small lattice mismatch to graphene and to close-packed surfaces of fcc-Ni(111) and hcp-Co(0001). Epitaxial deposition of h-BN on ferromagnetic metals is aimed at small interface scattering of charge and spin carriers. We report on the controlled growth of h-BN/Ni(111) by means of molecular beam epitaxy (MBE). Structural and electronic properties of this system are investigated using cross-section transmission electron microscopy (TEM) and electron spectroscopies which confirm good agreement with the properties of bulk h-BN. The latter are also corroborated by density functional theory (DFT) calculations, revealing that the first h-BN layer at the interface to Ni is metallic. Our investigations demonstrate that MBE is a promising, versatile alternative to both the exfoliation approach and chemical vapour deposition of h-BN

POSSIBILITIES OF FORMATION OF BRIGHT EBIC CONTRASTS DUE TO CRYSTAL DEFECTS IN SILICON

Besides the usual, well understood dark recombination contrasts, also bright EBIC contrasts can be found at extended crystal defects in silicon. Often they appear as bright haloes around dark contrasts, but sole bright contrats are observed, too

HIGH VOLTAGE ELECTRON MICROSCOPY AND SCANNING ELECTRON MICROSCOPY (EBIC MODE) OF THE SAME DISLOCATION

Les études des défauts cristallins, spécialement des dislocations situées près des jonctions p-n formées au moyen de la diffusion dans des échantillons de silicium, ainsi que des dislocations situées prés des jonctions p-n induites par le champ électrique en des structures MIS spéciales, qui sont effectuées utilisant une combinaison : microscopie électronique à balayage (mode EBIC) et microscopie électronique à haute tension, ont révélé une corrélation directe entre les défauts cristallins individuels et leur activité électrique. Les résultats obtenus montrent que plus cette "activité" est grande, plus prononcée est la "décoration" des défauts par des agglomérations d'impuretés.Investigations of crystal defects, especially dislocations near diffused p-n junctions in silicon materials and near field-induced p-n junctions in special MIS structures, carried out by a combination of scanning electron microscopy (EBIC mode) and high-voltage electron microscopy, have revealed a direct correlation between individual crystal defects and their electrical activity. The achieved results point to the fact that this "activity" is the higher the stronger the imaged defects are decorated by impurity agglomerates