Saskia Schimmel

Saskia Schimmel
Friedrich-Alexander-University of Erlangen-Nürnberg | FAU

Dr.-Ing.

About

22
Publications
1,937
Reads
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248
Citations
Citations since 2016
12 Research Items
225 Citations
201620172018201920202021202201020304050
201620172018201920202021202201020304050
201620172018201920202021202201020304050
201620172018201920202021202201020304050
Introduction
My interest in the physics and applications of functional materials, in particular materials for electronic devices, has triggered my interest in the synthesis and crystal growth of materials for electronics and optoelectronics. A current focus of my research is the further development of fundamental understanding and technology of the ammonothermal method as a tool for the synthesis and crystal growth of nitride materials, partially via in situ monitoring techniques and numerical simulations.
Additional affiliations
August 2021 - July 2022
Friedrich-Alexander-University of Erlangen-Nürnberg
Position
  • Postdoc Position
May 2019 - May 2021
Nagoya University
Position
  • PostDoc Position
October 2018 - March 2019
Lehigh University
Position
  • Research Associate
Education
October 2012 - December 2018
October 2010 - July 2012
Friedrich-Alexander-University of Erlangen-Nürnberg
Field of study
  • Materials Science and Engineering
October 2007 - October 2010
Friedrich-Alexander-University of Erlangen-Nürnberg
Field of study
  • Materials Science and Engineering

Publications

Publications (22)
Article
Quantitative data on the solubility of GaN in supercritical ammonia using NH4F as mineralizer are reported. The solubility is determined by in situ x-ray imaging of the dissolution of GaN single crystals. First solubility values obtained by this method with NH4Cl as mineralizer are presented and discussed with respect to existing literature data. M...
Article
In this contribution, first synthesis of semiconducting ZnSiN2 and ZnGeN2 from solution is presented with supercritical ammonia as solvent and KNH2 as ammonobasic mineralizer. The reactions were conducted in custom-built high-pressure autoclaves made of nickel-based superalloy. The nitrides were characterized by powder X-ray diffraction and their c...
Article
Full-text available
Thermal boundary conditions for numerical simulations of ammonothermal GaN crystal growth are investigated. A global heat transfer model that includes the furnace and its surroundings is presented, in which fluid flow and thermal field are treated as conjugate in order to fully account for convective heat transfer. The effects of laminar and turbul...
Article
Full-text available
Numerical simulations are a valuable tool for the design and optimization of crystal growth processes because experimental investigations are expensive and access to internal parameters is limited. These technical limitations are particularly large for ammonothermal growth of bulk GaN, an important semiconductor material. This review presents an ov...
Article
Full-text available
For the fundamental understanding and the technological development of the ammonothermal method for the synthesis and crystal growth of nitrides, an in situ monitoring technique for tracking mass transport of the nitride throughout the entire autoclave volume is desirable. The feasibility of using high-energy computed tomography for this purpose wa...
Article
Full-text available
The Special Issue on “Artificial Intelligence for Crystal Growth and Characterization” comprises six original articles in this emerging field of research [...]
Chapter
As the ammonothermal method often requires technically challenging conditions such as high temperature, high pressure and reaction media that are rather corrosive towards most metals (see Chap. 11), the further development of ammonothermal process equipment is of vital importance for tapping the full potential of the ammonothermal method. Suitable...
Chapter
X-ray based in situ monitoring techniques for ammonothermal processes are reviewed. Technological aspects are discussed, including general aspects of in situ X-ray visualization technology as well as the corrosion resistance of prospective materials for X-ray transparent windows under ammonothermal conditions (for more comprehensive information on...
Article
Full-text available
A variety of functional nitride materials, including the important wide bandgap semiconductor GaN, can be crystallized in exceptionally good structural quality by the ammonothermal method. However, the further development of this method is hindered by a lack of access to internal process parameters including fluid temperatures, flow stability and r...
Thesis
The main objective of this work was to establish x-ray based in situ measurement tech-nologies as a tool for investigating ammonothermal reaction processes. For this pur-pose, equipment for integrating ammonothermal experiments at temperatures up to 600 °C and pressures up to 300 MPa with in situ x-ray measurements had to be devel-oped. These exper...
Article
Formation and transport of Ga-containing intermediates are essential for ammonothermal bulk growth of GaN. In this work, in situ x-ray transmission measurements are established as a tool for monitoring face-selective dissolution of GaN crystals as well as the Ga-concentration in the fluid. The accuracy of concentration determination by x-ray transm...
Article
Solubility and dissolution kinetics of GaN are investigated, as they represent essential parameters for ammonothermal crystal growth of GaN. In situ X-ray imaging is applied to monitor the dissolving crystal. Both ammonoacidic and ammonobasic conditions are investigated. Compared to NH4F, the dissolution is generally much slower using NaN3 minerali...
Article
The chemical stability of diamond, silicon carbide, vitreous carbon, and boron carbide in supercritical ammonia containing different mineralizers was investigated. The materials were found to show good corrosion resistance in the presence of selective or all tested mineralizers. Diamond was found to be virtually inert in both ammonoacidic and ammon...
Article
The ammonoacidic crystal growth is a comprehensive method for the synthesis of novel compounds like nitrides or amindes but also for the growth of bulk single crystals like gallium or aluminum nitride for power electronics and photonics. In this report we describe a novel liner technology for growth autoclaves, showing high potential for several re...
Article
In-situ X-ray visualization of hydrothermal growth of silicalite-1 is applied as an intermediate step for developing X-ray in-situ visualization techniques for ammonothermal growth of nitride materials. In-situ X-ray imaging of silicalite-1 crystals grown by the bulk material dissolution technique (Shimizu and Hamada, Angew. Chem., Int. Ed. 38, 272...
Article
Silicon carbide (SiC) has played a key role in power electronics thanks to its unique physical properties like wide bandgap, high breakdown field, etc. During the past decade, SiC is also becoming more and more active in optoelectronics thanks to the progress in materials growth and nanofabrication. This paper will review the advances in fluorescen...
Article
Full-text available
The nucleation and bulk growth of polycrystalline SiC in a 2 inch PVT setup using isostatic and pyrolytic graphite as substrates was studied. Textured nucleation occurs under near-thermal equilibrium conditions at the initial growth stage with hexagonal platelet shaped crystallites of 4H, 6H and 15R polytypes. It is found that pyrolytic graphite re...
Article
Full-text available
Donor-acceptor co-doped SiC is a promising light converter for novel monolithic all-semiconductor white LEDs due to its broad-band donor-acceptor pair luminescence and potentially high internal quantum efficiency. Besides sufficiently high doping concentrations in an appropriate ratio yielding short radiative lifetimes, long nonradiative lifetimes...
Article
Polycrystalline doped SiC act as source for fluorescent SiC. We have studied the growth of individual grains with different polytypes in the source material. We show an evolution and orientation of grains of different polytypes in polycrystalline SiC ingots grown by the Physical Vapor Transport method. The grain influence on the growth rate of f...
Article
Homoepitaxial layers of fluorescent 4H-SiC were grown on 4 degree off-axis substrates by sublimation epitaxy. Luminescence in the green spectral range was obtained by co-doping with nitrogen and boron utilizing donor-acceptor pair luminescence. This concept opens possibilities to explore green light emitting diodes using a new materials platform...
Article
Bulk-like 3C-SiC was grown on 1.2 degrees low off-axis 6H-SiC substrates using a sublimation epitaxy technique. The effects of temperature ramp-up and increase in layer thickness on the 3C-SiC domain formation were explored. The temperature ramp-up had no significant effect on the domain size. The domain size was considerably increased and the c...
Article
Structural defects in aluminium nitride (AlN) get visible in panchromatic cathodoluminescence (CL) maps as luminescence at 340 nm and 630 nm is locally enhanced. Low-angle grain boundaries (LAGBs) and dislocations can be detected as long as they are sufficiently decorated and the defect-related contrast is higher than local variations in background...

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Projects

Projects (4)
Project
Machine learning and artificial intelligence methods in general have recently reached a stage at which they become increasingly useful to researchers in other fields. The goal of this Special Issue is to promote the use of those methods in the field of synthesis and characterization of crystalline materials. Further information: https://www.mdpi.com/journal/crystals/special_issues/artificialintelligence_crystal