A5026144800- Ferroelectric and Negative Capacitance Devices
- Semiconductor materials and devices
- MXene and MAX Phase Materials
- Advanced Memory and Neural Computing
- Electronic and Structural Properties of Oxides
- Ferroelectric and Piezoelectric Materials
- Textile materials and evaluations
- Advanced ceramic materials synthesis
- Metal and Thin Film Mechanics
- Ion-surface interactions and analysis
- Inorganic Chemistry and Materials
- Diamond and Carbon-based Materials Research
- Natural Fiber Reinforced Composites
- Molecular Junctions and Nanostructures
- Industrial Vision Systems and Defect Detection
- Advanced Chemical Physics Studies
- Machine Learning in Materials Science
- Advanced Materials Characterization Techniques
University of Bayreuth
2024
Munich University of Applied Sciences
2015-2019
University of Connecticut
2019
NaMLab (Germany)
2016-2017
The structural, thermal, and dielectric properties of the ferroelectric phase HfO2, ZrO2, Hf0.5Zr0.5O2 (HZO) are investigated with carefully validated density functional computations. We find that free bulk energy orthorhombic Pca21 is unfavorable compared to monoclinic P21/c Pbca for all stoichiometries in Hf1−xZrxO2 system. To explain existence nanoscale thin films, we explore Gibbs/Helmholtz energies as a function stress film strain them unlikely become minimal HZO films technological...
Recent discovery of ferroelectricity in HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> thin films paved the way for demonstration ultra-scaled 28 nm Ferroelectric FETs (FeFET) as non-volatile memory (NVM) cells [1]. However, such small devices are inevitably sensible to granularity polycrystalline gate oxide film. Here we report first time evidence single ferroelectric (FE) domain switching scaled devices. These properties sensed...
Even though many studies on the field cycling behavior of ferroelectric hafnium oxide have recently been published, issue is still not fully understood. The initial increase polarization during first cycles explained by different theoretical and empirical approaches. Field‐induced phase changes as well oxygen vacancy diffusion from interfacial layers toward bulk are discussed. Trapped charges mentioned might cause a shift hysteresis along voltage axis called imprint. various connect this...
III-valent dopants have shown to be most effective in stabilizing the ferroelectric, crystalline phase atomic layer deposited, polycrystalline HfO2 thin films. On other hand, such are commonly used for tetragonal and cubic stabilization ceramic HfO2. This difference impact has not been elucidated so far. The prospect is a suitable doping produce ferroelectric ceramics with technological impact. In this paper, we investigate of Al, Y, La doping, which experimentally proven stabilize Pca21...
Abstract The outstanding remanent polarization of 40 µC cm –2 reported for a 10 nm thin La:HfO 2 film in 2013 has attracted much attention. However, up to now, no explanation this large been presented. Density functional theory and X‐ray diffraction are used shine light onto three major aspects that impact the macroscopically observed polarization: phase fraction, spontaneous polarization, crystallographic texture. calculations show ( P s ) is indeed bit larger than other HfO ‐ or ZrO ‐based...
The ferroelectric properties of nanoscale silicon doped HfO$_2$ promise a multitude applications ranging from memory to energy-related applications. reason for the unexpected behavior has not been clearly proven and presumably include contributions size effects doping effects. Silicon incorporation in is investigated computationally by first-principles using different density functional theory (DFT) methods. Formation energies interstitial substitutional paired with without an oxygen vacancy...
Size effects from surface or interface energy play a pivotal role in stabilizing the ferroelectric phase recently discovered thin film Zirconia-Hafnia. However, sufficient quantitative understanding has been lacking due to interference with effect dopants. For important class of undoped Hf1–xZrxO2, stability model based on free Density functional theory (DFT) and values adapted sparse experimental theoretical data successful describe key properties available data. Since surfaces interfaces...
Different dopants with their specific dopant concentration can be utilized to produce ferroelectric HfO$_2$ thin films. In this work it is explored for the example of Sr in a comprehensive first-principles study. Density functional calculations reveal structure, formation energy and total related defects HfO$_2$. We found charge compensated defect including an associated oxygen vacancy Sr$_\text{Hf}$V$_\text{O}$ strongly favour non-ferroelectric, tetragonal P4$_\text{2}$/mnc phase...
Abstract Insight into the origin of process-related properties like small-scale inhomogeneities is key for material optimization. Here, we analyze DFT calculations randomly doped HfO 2 structures with Si, La, and V O relate them to kind production process. Total energies relevant ferroelectric Pbc2 1 phase are compared competing crystallographic phases under influence arising local in a coarse-grained approach. The interaction among dopants adds statistical effect from random positioning...
The discovery of ferroelectricity in HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and ZrO based dielectrics enabled the introduction these materials highly scalable non-volatile memory devices. Typical cells are using a capacitor or transistor as storage device. These scaled devices sensitive to local structure material, here granularity dielectric doped layer, varying ferroelectric properties. Detailed studies conducted correlate...
The past two decades have witnessed a tremendous number of computational predictions hydride-based (phonon-mediated) superconductors, mostly at extremely high pressures, i.e., hundreds gigapascals. These discoveries were strongly driven by Migdal–Éliashberg theory (and its first-principles implementations) for electron–phonon interactions, the key concept phonon-mediated superconductivity. Dozens experimentally synthesized and characterized, triggering not only enormous excitement in...
Molecular-like carbon-nitrogen complexes in GaAs are investigated both experimentally and theoretically. Two characteristic high-frequency stretching modes at 1973 2060 cm−1, detected by Fourier transform infrared absorption (FTIR) spectroscopy, appear carbon- nitrogen-implanted annealed layers. From isotopic substitution, it is deduced that the chemical composition of underlying CN2 C2N, respectively. Piezospectroscopic FTIR measurements reveal centers have tetragonal symmetry. For density...
The nitrogen-vacancy (NV) center occurs in GaAs bulk crystals doped or implanted with nitrogen. local vibration of nitrogen gives rise to a sharp infrared absorption band at 638 cm$^{-1}$, exhibiting fine structure due the different masses neighboring $^{69}$Ga and $^{71}$Ga host isotopes. Piezospectroscopic investigations crystallographic <100> direction prove that has C$_\text{3v}$ point symmetry, which is weakly perturbed by isotope effect. stress-induced shifts some components show an...