Split-off dimer defects on the Si(001)2x1 surface

The hole doped Si(111)(2root3x2root3)R30(degrees)-Sn interface exhibits a symmetry-breaking insulator-insulator transition below 100 K that appears to be triggered by electron tunneling into the empty surface-state bands. No such transition is seen in electron-doped systems. To elucidate the nature and driving force of this phenomenon, the structure of the interface must be resolved. Here we report on an extensive experimental and theoretical study, including scanning tunneli...

Over the last two decades, scanning tunnelling microscopy (STM) has become one of the most important ways to investigate the structure of crystal surfaces. STM has helped achieve remarkable successes in surface science such as finding the atomic structure of Si(111) and Si(001). For high-index Si surfaces the information about the local density of states obtained by scanning does not translate directly into knowledge about the positions of atoms at the surface. A commonly acc...

We report on a combined scanning tunneling microscopy and density functional theory calculation study of the SrTiO3(110)-(4 x 1) surface. It is found that antiphase domains are formed along the [1-10]-oriented stripes on the surface. The domain boundaries are decorated by defects pairs consisting of Ti2O3 vacancies and Sr adatoms, which relieve the residual stress. The formation energy of, and interactions between, vacancies result in a defect superstructure. It is suggested ...

Recent experimental studies have shown that well-annealed, unstrained Si(105) surfaces appear disordered and atomically rough when imaged using scanning tunnelling microscopy (STM). We construct new models for the Si(105) surface that are based on single- and double-height steps separated by Si(001) terraces, and propose that the observed surface disorder of Si(105) originates from the presence of several structural models with different atomic-scale features but similar ener...

An ideal one-dimensional electronic system is formed along atomic chains on Au-decorated vicinal silicon surfaces but the nature of its low temperature phases has been puzzled for last two decades. Here, we unambiguously identify the low temperature structural distortion of this surface using high resolution atomic force microscopy and scanning tunneling microscopy. The most important structural ingredient of this surface, the step-edge Si chains are found to be strongly buck...

We use scanning tunneling microscopy (STM) and Auger electron spectroscopy to study the behavior of adsorbed phosphine (PH$_{3}$) on Si(001), as a function of annealing temperature, paying particular attention to the formation of the Si-P heterodimer. Dosing the Si(001) surface with ${\sim}$0.002 Langmuirs of PH$_{3}$ results in the adsorption of PH$_{x}$ (x=2,3) onto the surface and some etching of Si to form individual Si ad-dimers. Annealing to 350$^{\circ}$C results in th...

Deep defects in silicon carbide (SiC) possess atom-like electronic, spin and optical properties, making them ideal for quantum-computing and -sensing applications. In these applications, deep defects are often placed within fabricated nanostructures that modify defect properties due to surface and quantum confinement effects. Thus far, theoretical studies exploring deep defects in SiC have ignored these effects. Using density functional theory, this work demonstrates site-dep...

The basic properties of point defects (atomic geometry, the position of charge-transfer levels, and formation energies) on the (110) surface of GaAs, GaP, and InP have been calculated employing density-functional theory. Based on these results we discuss the electronic properties of surface defects, defect segregation, and compensation.

The bonding pattern of a covalent semiconductor is disrupted when a surface is cut while keeping a rigid (truncated bulk) geometry. The covalent bonds are partly reformed (with a sizeable energy gain) when reconstruction is allowed. We show that the ``electron localization function'' (ELF)---applied within a first--principles pseudopotential framework---provides un unprecedented insight into the bonding mechanisms. In the unreconstructed surface one detects a partly metallic ...

Two-dimensional (2D) materials have emerged as promising platforms for quantum technologies and optoelectronics, with defects playing a crucial role in their properties. We present a comprehensive density functional theory study of silicon and carbon vacancies in monolayer silicon carbide (1L-SiC), a wide-bandgap 2D semiconductor with potential for room-temperature quantum applications. Using PBE, SCAN, r$^2$SCAN, and HSE06 functionals, we reveal distinct characteristics betw...