arXiv subjects

P. Udvarhelyi

Publications and source records attributed to P. Udvarhelyi.

4 recordsLinked to original sources

arXiv2025

Quantum enhanced electric field mapping within semiconductor devices

Semiconductor components based on silicon carbide (SiC) are a key component for high-power electronics. Their behavior is determined by the interplay of charges and electric fields, which is typically described by modeling and simulations that are calibrated by nonlocal electric properties. So far, there are no experimental methods that allow for the 3D mapping of both the electric field and the concentrations of free charge carriers inside an electronic device. To fulfill this information gap, we propose an operando method that utilizes single silicon vacancy (VSi) centers in 4H-SiC. The VSi centers are at various positions in the intrinsic region of a pin-diode. To monitor the local static electric field, we perform Stark shift measurements based on photoluminescence excitation (PLE), which allows us to infer the expansion of the depletion zone and therefore to determine the local concentration of dopants. Besides this, we show that our measurements allow us to additionally obtain the local concentration of free charge carriers. The method presented here therefore paves the way for a new quantum-enhanced electronic device technology, capable of mapping the interplay of mobile charges and electric fields in a working semiconductor device with nanometer precision.

quant-ph↗

arXiv2023

Vacancy-related color centers in twodimensional silicon carbide monolayers

Basic vacancy defects in twodimensional silicon carbide (2D-SiC) are examined by means of density functional theory calculations to explore their magneto-optical properties as well as their potential in quantum technologies. In particular, the characteristic hyperfine tensors and optical excited states of carbon-vacancy, silicon-vacancy, and carbon antisite-vacancy pair defects in 2D-SiC are determined that are the key fingerprints of these defects that may be observed in electron paramagnetic resonance and photoluminescence experiments, respectively. Besides the fundamental characterization of the most basic native defects, we show that the negatively charged carbon antisite-vacancy defect is a promising candidate for realizing a near-infrared single-photon quantum emitter with spin doublet ground state, where the negative charge state may be provided by nitrogen doping of 2D-SiC. We find that the neutral carbon-vacancy with spin triplet ground state might be used for quantum sensing with a broad emission in the visible.

cond-mat.mtrl-sci↗

arXiv2023

Optically-active spin defects in few-layer thick hexagonal boron nitride

Optically-active spin defects in hexagonal boron nitride (hBN) are promising quantum systems for the design of two-dimensional quantum sensing units offering optimal proximity to the sample being probed. In this work, we first demonstrate that the electron spin resonance frequencies of boron vacancy centres (V$_\text{B}^-$) can be detected optically in the limit of few-atomic-layer thick hBN flakes despite the nanoscale proximity of the crystal surface that often leads to a degradation of the stability of solid-state spin defects. We then analyze the variations of the electronic spin properties of V$_\text{B}^-$ centres with the hBN thickness with a focus on (i) the zero-field splitting parameters, (ii) the optically-induced spin polarization rate and (iii) the longitudinal spin relaxation time. This work provides important insights into the properties of V$_\text{B}^-$ centres embedded in ultrathin hBN flakes, which are valuable for future developments of foil-based quantum sensing technologies.

quant-ph↗

arXiv2023

A planar defect spin sensor in a two-dimensional material susceptible to strain and electric fields

The boron-vacancy spin defect ($\text{V}_\text{B}^{-}$) in hexagonal boron nitride (hBN) has a great potential as a quantum sensor in a two-dimensional material that can directly probe various external perturbations in atomic-scale proximity to the quantum sensing layer. Here, we apply first principles calculations to determine the coupling of the $\text{V}_\text{B}^{-}$ electronic spin to strain and electric fields. Our work unravels the interplay between local piezoelectric and elastic effects contributing to the final response to the electric fields. The theoretical predictions are then used to analyse optically detected magnetic resonance (ODMR) spectra recorded on hBN crystals containing different densities of $\text{V}_\text{B}^{-}$ centres. We prove that the orthorhombic zero-field splitting parameter results from local electric fields produced by surrounding charge defects. By providing calculations of the spin-strain and spin-electric field couplings, this work paves the way towards applications of $\text{V}_\text{B}^{-}$ centres for quantitative electric field imaging and quantum sensing under pressure.

quant-ph↗