Showing papers by "Oliver Ambacher published in 2007"
TL;DR: In this article, the basic operation principle for MEMS with wide band gap semiconductors is described, and the first applications of SiC based MEMS are demonstrated, and innovative MEMS and NEMS devices are reviewed.
Abstract: With the increasing requirements for microelectromechanical systems (MEMS) regarding stability, miniaturization and integration, novel materials such as wide band gap semiconductors are attracting more attention. Polycrystalline SiC has first been implemented into Si micromachining techniques, mainly as etch stop and protective layers. However, the outstanding properties of wide band gap semiconductors offer many more possibilities for the implementation of new functionalities. Now, a variety of technologies for SiC and group III nitrides exist to fabricate fully wide band gap semiconductor based MEMS. In this paper we first review the basic technology (deposition and etching) for group III nitrides and SiC with a special focus on the fabrication of three-dimensional microstructures relevant for MEMS. The basic operation principle for MEMS with wide band gap semiconductors is described. Finally, the first applications of SiC based MEMS are demonstrated, and innovative MEMS and NEMS devices are reviewed.
352 citations
TL;DR: In this article, fabrication, operation, and sensing properties of ceramic wide band gap (AlN and SiC) NEMS sensors are demonstrated, where the internal strain of such beams can be used to improve the resonant performance of the devices.
Abstract: Resonant nanoelectromechanical systems (NEMS) are promising devices for a new class of ultrafast, highly sensitive devices. In this work, fabrication, operation, as well as sensing properties of ceramic wide band gap (AlN and SiC) NEMS sensors will be demonstrated. The internal strain of such beams can be used to improve the resonant performance of the devices. Special attention is drawn to the operation of such sensors in air, which represents a viscous medium and reduces drastically the quality factor of NEMS resonators from 104 to 105 in vacuum to 10–300 in air. This intrinsic property limits the sensitivity for applications in air and has to be taken into account in the design of the sensors. For such resonators, the main problems for an operation in viscous media will be discussed in more detail, and the sensing properties for mass loading, temperature and pressure are exemplarily demonstrated.
102 citations
TL;DR: In this article, high-quality InN nanocolumns grown by molecular beam epitaxy on n-type Si(111) have been electrically characterized by atomic force microscopy.
Abstract: High-quality InN nanocolumns grown by molecular beam epitaxy on n-type Si(111) have been electrically characterized by atomic force microscopy. Current-voltage characteristics were measured on InN nanocolumns with similar heights but different diameters. The conductivity scales the nanocolumns reciprocal diameter, pointing to the nanocolumn lateral surface as the main conduction path. These results, opposing those found in undoped GaN nanocolumns where the conductivity is rather independent of the diameter (conduction through the volume), agree well with a model that predicts electron accumulation by Fermi level pinning within the conduction band on nonpolar (m plane) InN surfaces reconstructed under In-rich conditions.
79 citations
TL;DR: In this article, the impact of typical device processing steps (KOH, HCl, HF wet chemical etching, SF 6 and Cl plasma etching) on the surface properties (roughness, chemical composition, contact angle to water) of group III-nitride based chemical sensors is investigated with emphasis on the electrical performance of the sensor and the biocompatibility.
Abstract: The impact of typical device processing steps (KOH, HCl, HF wet chemical etching, SF 6 and Cl plasma etching) on the surface properties (roughness, chemical composition, contact angle to water) of group III-nitride based chemical sensors is investigated with emphasis on the electrical performance of the sensor and the biocompatibility. An AlGaN/GaN high electron mobility transistor serves as basic sensing device. For our studies, the widely distributed mammalian cell cultures HEK 293FT and CHO-K1 are used as biological model systems. The processing of the devices has only little influence on the cell growth onto the sensor, which is in all cases superior to that on silicon surfaces. Fluorine dry etching leads to oxidation and smoothing of the surface, thus, improving the electrical properties of the AlGaN/GaN sensor. In contrast, autoclave treatment enhances the carbon contamination with negative impact on the sensor properties and increased the contact angle to water, which can be used as indicator for the state of the sensor surface. For all other treatments the contact angle recaptures a stable value of about 50 ± 5° after exposure to air or water droplets for some hours due to contamination by hydrocarbons.
79 citations
TL;DR: In this article, the authors integrated ultrathin layers of In2O3 nanoparticles and a GaInN∕GaN based blue light emitting diode (LED) on a single sensor chip.
Abstract: There is a high demand for compact low-cost ozone sensors. It has been shown recently that In2O3 nanolayers can act as ozone sensitive films activated at room temperature by ultraviolet light. In the present work, the authors integrate ultrathin layers of In2O3 nanoparticles and a GaInN∕GaN based blue light emitting diode (LED) on a single sensor chip. The integrated sensor was found to be sensitive to O3 concentrations as low as ∼40ppb. These results demonstrate that by integrating GaInN∕GaN based blue LEDs and metal oxide sensing layers back to back on a single chip, compact and robust gas sensors can be realized.
77 citations
TL;DR: In this paper, the complex dielectric function (DF) for hexagonal alloys with N-face polarity from near-infrared into the vacuum ultraviolet spectral region was determined by a fit of the third derivative of the DF.
Abstract: Spectroscopic ellipsometry is applied in order to determine the complex dielectric function (DF) for In-rich ${\mathrm{In}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{N}$ alloys with N-face polarity from near-infrared into the vacuum ultraviolet spectral region. The results are compared to corresponding data for metal-face films. The optical properties of both types of hexagonal films agree in the essential features which emphasizes that the extracted DFs do not depend on the polarity but represent therefore bulk characteristics. Besides the band gap, five critical points of the band structure are clearly resolved within the composition range of $1\ensuremath{\geqslant}x\ensuremath{\geqslant}0.67$. Their transition energies are determined by a fit of the third derivative of the DF. With increasing Ga content, all transitions undergo a continuous shift to higher energies characterized by small bowing parameters. Model calculations of the imaginary part of the DF close to the band gap that take the influence of band filling and conduction-band nonparabolicity into account are presented. A comparison to the experimental data yields the position of the Fermi energy. With the calculated values for the carrier-induced band-gap renormalization and the Burstein-Moss shift, the zero-density values for the fundamental band gaps are obtained. Their dependence on the alloy composition is described by a bowing parameter of $b=1.72\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$.
52 citations
TL;DR: In this paper, the conduction-band dispersion relation for 12 III-V and II-VI semiconductors with zinc-blende crystal structure and deduced the corresponding nonparabolicity coefficients.
Abstract: Adjusting calculated spectra of the imaginary part ${\ensuremath{\epsilon}}_{2}$ of the dielectric function to experimental ones in a spectral region close to and above the fundamental absorption edge, we determined the conduction-band dispersion relation for 12 III-V and II-VI semiconductors with zinc-blende crystal structure and deduced the corresponding nonparabolicity coefficients This yields an experimental determination of the conduction-band nonparabolicity and momentum electron effective mass as a function of the wave vector and free electron concentration For most of the semiconductors, we present experimental data extended to electron energies between 06 and $22\phantom{\rule{03em}{0ex}}\mathrm{eV}$, which are significantly higher than those achievable by doping or in magnetic fields In addition, examination of experimental dielectric functions reported by various authors showed that the magnitude of ${\ensuremath{\epsilon}}_{2}$ is overestimated in the existing literature data for GaSb, ZnTe, ZnS, and CdSe, probably due to the neglect or incorrect treatment of possible overlayers
46 citations
TL;DR: In this article, a semiconductor fabrication process has been applied to prepare resonant AlN and SiC beams operating at frequencies between 0.1 and 2.1 MHz, and the metallized beams were actuated in a permanent magnetic field of about 0.5 T by the Lorentz force.
Abstract: MEMS resonators bear great potential for applications as RF sensors, filters and oscillators, e.g., in life sciences or information technology. A semiconductor fabrication process has been applied to prepare resonant AlN and SiC beams operating at frequencies between 0.1 and 2.1 MHz. The metallized beams were actuated in a permanent magnetic field of about 0.5 T by the Lorentz force. For systematic studies of the resonant frequencies and quality factors, the induced voltage was measured using time domain and frequency domain techniques. Resonator geometry, material and ambient pressure were varied to attain a generalized understanding of the RF performance. The dependence of the resonant frequency on tensile axial strain has been derived analytically and extended to include highly strained beams. Based on these formulas, accurate detection of the residual layer strain after fabrication is presented. To describe the quality factor a chain of beads model has been applied successfully. The influences of the beam width and the pressure-dependent viscosity on the model parameters are analyzed.
38 citations
TL;DR: In this article, the morphology and surface electronic structure of indium nitride films grown by plasma-induced molecular beam epitaxy have been studied using atomic force microscopy as well as X-ray and ultraviolet photoelectron spectroscopy.
38 citations
TL;DR: In this paper, the intermediate indium oxide layer presents a body centered cubic (bcc) structure with bcc-In2O3(001)‖Al2O 3(0001) plane relationship, which offers a promising expectation to obtain high quality cubic InN layers superior to other highly mismatched cubic substrates used previously.
Abstract: Cubic InN layers were grown by molecular beam epitaxy on buffer layers of indium oxide prepared onto sapphire (0001) substrates. The structure was analyzed by means of electron diffraction and transmission electron microscopy. The intermediate indium oxide layer presents a body centered cubic (bcc) structure, with bcc-In2O3(001)‖Al2O3(0001) plane relationship. Thereupon, a zinc-blende phase of InN (001) was grown with a reticular misfit of 1.6% and a significant reduction of mismatch-related defects. This good coherence offers a promising expectation to obtain high quality cubic InN layers superior to other highly mismatched cubic substrates used previously.
37 citations
TL;DR: In this paper, a room temperature ozone induced oxidation of thin InN films is proposed to improve the electric transport properties of InN layers and the sheet carrier density is reduced by a value which is in the order of the electron concentration of an untreated InN surface.
Abstract: A room temperature ozone induced oxidation of thin InN films is proposed to improve the electric transport properties. The sheet carrier density is reduced upon oxidation by a value which is in the order of the electron concentration of an untreated InN surface. Thus, ozone effectively passivates the surface defect states on InN and might be an effective method to prepare InN films for electronic applications. A model for the improved electron transport properties is proposed taking into account the decreased surface band bending and the decreased influence of surface electrons on the net mobility of InN layers.
TL;DR: Tuning of structural and electrical properties of indium oxide (In 2 O 3 ) films by means of metal organic chemical vapor deposition is demonstrated in this paper, where phase selective growth of rhombohedral and body-centered cubic polytypes on (0001) sapphire substrates was obtained by adjusting the substrate temperature and trimethylindium flow rate.
TL;DR: In this article, the effect of substrate temperature and reactor pressure on indium oxide thin film growth and structural properties in the range of 250-350°C and 5.6 × 10 − 3 ǫ cm was investigated.
TL;DR: In this paper, a grain boundary model was proposed to understand the photoreduction and oxidation mechanism for the nanoparticle layers, and it was suggested that the nanoparticles are reactivated throughout the layer.
Abstract: In2O3 nanoparticles were synthesized at low substrate temperatures by the metal organic chemical vapor deposition technique. Nanoparticles with a mean diameter from 3 to 33 nm can be obtained by varying the growth temperature. Photoreduction and oxidation studies were carried out for particle-containing layers exhibiting a resistance change of more than five orders of magnitude after ultraviolet irradiation and oxidation by ozone. A grain boundary model was proposed to understand the photoreduction and oxidation mechanism for the nanoparticle layers. It was suggested that by photoreduction the nanoparticles are reactivated throughout the layer. The Schottky barrier between the nanoparticles decreases inducing a reduction of the space-charge-limited region. After oxidation, a completely depleted space-charge region covering the whole volume of In2O3 nanoparticles is formed. Furthermore, the bulk diffusion process dominates the response of thick layers during the oxidation process. By decreasing the layer t...
TL;DR: In this article, a growth model was proposed to explain the formation of domain boundaries and stacking faults formed during the coalescence of wurtzite-III-nitride epitaxy, and it was shown that two adjacent and tilted, hexagonal-shaped 2H domains may form a noncoherent boundary explicitly along a polygonal plane.
Abstract: In this work, coalescence aspects of wurtzite-III-nitride epitaxy are addressed. The coalescence phenomena have been studied in thin epilayers by means of electron and atomic force microscopies, and electron and x-ray diffractions. This study generalizes the growth parameters responsible for the rapid coalescence of III-nitride films, and describes the coalescence qualitatively and, partly, analytically for the case of heteroepitaxy in nonequilibrium conditions. Coalescence time and the corresponding diffusion coefficients at elevated temperatures were estimated for GaN and InN depositions. The rate of coalescence has been found to impact on the structure and morphology of III-nitride epilayers. A simple growth model was suggested to explain the formation of domain boundaries and (0001) stacking faults formed during the coalescence. In particular, it is shown that two adjacent and tilted, hexagonal-shaped 2H domains may form a noncoherent boundary explicitly along a {11¯00} plane. We also suggest that the...
TL;DR: In this paper, single crystalline cubic In2O3 (111) films were epitaxially grown on hexagonal InN (0001) epilayers and the epitaxial relationship between the film and the template was determined.
Abstract: Single crystalline In2O3 is a prospective material to be used as a gate dielectric in InN based field effect transistors (FETs) This work addresses structural investigations of In2O3∕InN heterostuctures for metal-oxide-semiconductor FET devices Single crystalline cubic In2O3 (111) films were epitaxially grown on hexagonal InN (0001) epilayers The epitaxial relationship between the film and the template was determined as In2O3[111]‖InN[0001] and In2O3[101¯]‖InN⟨112¯0⟩ with an effective lattice mismatch of 214% On the basis of the structural investigations, a phenomenological model for the growth of In2O3 on InN (0001) is proposed
TL;DR: In this article, the authors measured the conductivity of gallium nitride (GaN) nanocolumns with a length up to 1μm and a diameter of about 30-80nm.
Abstract: The electrical characterization of gallium nitride (GaN) nanocolumns with a length up to 1 μm and a diameter of about 30–80 nm grown on doped silicon is a challenge for nano analytics. To determine the conductivity of these nanocolumns, I – V characteristics were recorded by atomic force microscopy (AFM). To measure the conductivity of a single nanocolumn, a conductive AFM tip was placed at the top of the nanocolumn. The measured current/voltage characteristic of a single nanocolumn shows the typical performance of a Schottky contact, which is caused by the contact between the metallic AFM tip and the semiconductor material of the nanocolumn. The height of the Schottky barrier is dependent on the work function of the AFM tip metal used. The linear part of the curve was used to calculate the differential resistance, which was found to be about 13 Ω cm and slightly dependent on the diameter.
TL;DR: In this paper, the authors proposed a basic module for a novel nanowire-based nanoelectromechanical device, which will require the mechanical coupling of nanowires to an AlGaN/GaN heterostructure containing a polarization-induced 2D electron gas.
Abstract: We propose the development of a basic module for a novel nanowire-based nanoelectromechanical device, which will require the mechanical coupling of nanowires to an AlGaN/GaN heterostructure containing a polarization-induced 2D electron gas. The deflection of freestanding nanowires in a streaming liquid causes an additional strain in the AlGaN barrier which leads to a change in the resistance of the 2D electron gas. The basic structure, underlying theoretical considerations and first steps towards the realization of this new sensor concept are presented.
TL;DR: In this article, the authors measured terahertz radiation from InN and compared it with p-InAs excited by femtosecond optical pulses at 1060 and 800 nm.
Abstract: Terahertz radiation was measured from InN and compared to p-InAs excited by femtosecond optical pulses at 1060 and 800 nm. At 800 nm, atomically smooth InN with low background electron concentration exhibit higher THz emission than the highly effective material p-InAs. The higher THz emission efficiency of InN is caused by the absences of any intervalley scattering, which in the case of InAs increases the effective mass of the photo generated electrons and, thus, reduces the Dember field, which is responsible for THz emission. Consequently, InN is a promising material for THz emission; however, further improvement of the material quality (surface roughness and carrier concentration) is needed. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
TL;DR: In this article, the chemical and electron transport properties of oxidized indium nitride epilayers and indium oxide/indium nitric heterostructures are reported and the electron mobility for different dislocation densities and surface band bending values has been calculated.
Abstract: The chemical and electron transport properties of oxidized indium nitride epilayers and indium oxide/indium nitride heterostructures are reported. It is shown that the accumulation of electrons at the InN surface can be manipulated by the formation of a thin surface oxide layer using an ozone-assisted oxidation processing. It results in improved transport properties and in a reduction of the electron sheet concentration of the InN epilayer caused by a passivation of the surface donors and a shift of the electron density distribution peak from the surface toward the bulk InN. Using the ensemble Monte Carlo simulation method, the electron mobility for different dislocation densities and surface band bending values has been calculated. The theoretical results correlate well with our experimental data. In opposition to the ozone treatment, in epitaxial oxide/nitride heterojunctions the electron sheet concentration of InN raises due to the increasing band bending at the heterointerface affecting adversely the ...
TL;DR: In this paper, an adverse effect of broad-band trap distribution on the spectral, electrical, and time-response characteristics of AlGaN-based photodetectors was studied.
Abstract: Electrical properties and photoresponse of AlGaN based photodetectors were studied demonstrating an adverse effect of the broad-band trap distribution on the spectral, electrical, and time-response characteristics. It was found that n-type conduction mechanism is space charge limited indicating a strong carrier trapping effect. In particular, we show that dark current, photoresponsivity, and response time are determined by the slow-varying energy distribution of traps located above the equilibrium Fermi level. We demonstrate also that both the deep recombination centers and the localized shallow states do not impact the response time of the photodetector, and the persistent photocurrent effect is directly connected to the voltage-induced injection and trapping of the excess carriers.
TL;DR: In this paper, a complex three-dimensional, nanowire based nanoarchitecture is presented, which combines the benefits of three self-organization mechanisms to produce nanostructures, i.e., formation of nanoneedles, the droplet formation out of a thin metal film, and the vapor-liquid-solid growth of nanowires.
Abstract: A complex three-dimensional, nanowire based nanoarchitecture is presented, which can be processed by high-throughput bottom-up procedures without any high-resolution lithography. It combines the benefits of three self-organization mechanisms to produce nanostructures, i.e., the formation of nanoneedles, the droplet formation out of a thin metal film, and the vapor-liquid-solid growth of nanowires. The principle is demonstrated for a silicon based suspended nanowire web. Cell adherence on this assembly was found to be superior to other nanostructures. The possibility of fluid transport beneath the nanowire web enables improved microcatalyst principles and the realization of novel interfaces for biosensing or bioelectronics.
01 Jan 2007
TL;DR: In this article, the authors give some examples for the application of Auger electron spectroscopy to nanostructures mostly in group III-nitride semiconductor technologies: (i) nanowires, consisting of Si and AlN with diameters of about 20 to 200 nm; these nanwires and nanorods have been grown by different technologies and some of them are contacted on both ends by FIB grown Pt contacts,
Abstract: In modern nanotechnology analysis such methods are needed which are able to investigate extremely small volumes, thus surface sensitive techniques with a high spatial and depth resolution. Concerning the capability of high lateral and depth resolution, Auger electron spectroscopy (AES) is one of the outstanding analytical methods for nanotechnology. By field electron guns probe diameters below 10 nm are reached. Depth resolution of Auger electron spectroscopy, depending on the kinetic energy of the Auger electrons, is approximately 0.5 to 4 nm. Whereas large area AES has a detection limit of 0.1 at% it impairs for laterally highly resolved measurements. The article will give some examples for the application of Auger electron spectroscopy to nanostructures mostly in group III-nitride semiconductor technologies: (i) nanowires, consisting of Si and AlN with diameters of about 20 to 200 nm; these nanowires and nanorods have been grown by different technologies and some of them are contacted on both ends by FIB grown Pt contacts, (ii) nanoflowers,ie specially shaped up to 5µm sized networks of AlN nanowires of about 20 nm in diameter, (iii) segregation structures of Si of 200 nm width, grown during PIMBE AlN epitaxy on Si substrate. On the basis of these measurements the benefits and limits of Auger electron spectroscopy on nanostructures as well as some special effects which are characteristic especially for nanostructures, for instance resputtering and background signal contribution, are discussed. K e y w o r d s: nanotechnology, Auger electron spectroscopy, nanowires, nanoflowers, segregation
17 Dec 2007
TL;DR: In this paper, the authors used a permanent magnetic field of about 0.5 T by the Lorentz force to measure the resonant response in the frequency domain and found that the quality factor shows a high sensitivity on pressure.
Abstract: MEMS resonators bear great potential for applications as RF sensors, filters and oscillators, e.g., in life sciences or information technology. Resonant AlN and SiC beams with operation frequencies between 0.01 and 3.4 MHz have been prepared using a semiconductor fabrication process. The metallized beams were actuated in a permanent magnetic field of about 0.5 T by the Lorentz force. The resonant response was detected in the frequency domain. Resonator geometry and material were varied to attain a generalized understanding of the RF performance in dependence of the ambient pressure. In particular the quality factor shows a high sensitivity on pressure, allowing potential application as absolute pressure sensor. Theoretical models have been applied that match well to the measurement.
TL;DR: In this article, depletionmode 4H-SiC field effect transistors (FETs) were fabricated for use as gas sensors, and a mixture of indium oxide and tin oxide (SnO x ) was deposited by rf magnetron reactive sputtering as a gate material.
Abstract: We have fabricated depletion-mode 4H–SiC field effect transistors (FETs) for use as gas sensors. To enable sensitivity to NO x and O 2 gases, a mixture of indium oxide (InO x ) and tin oxide (SnO x ) was deposited by rf magnetron reactive sputtering as a gate material. The chemical composition of the deposited film was examined using Auger electron spectroscopy (AES) combined with depth profiling analysis. The response to NO x and O 2 gases was investigated as a function of operating temperature for different concentrations of the test gas. The maximal response to NO x and O 2 was observed at 350 and 400 °C, respectively.
TL;DR: In this paper, the formation and recombination rates of radical reaction depend on cellulose concentration in cellulose/NMMO solutions and additional ingredients, e.g., Fe(II) and propyl gallate.
Abstract: Degradation processes of N-methylmorpholine-N-oxide monohydrate (NMMO), cellulose and cellulose/NMMO solutions were studied by high performance liquid chromatography (HPLC) and electron spin resonance (ESR) spectroscopy. Kinetics of radical accumulation processes under UV (λ = 248 nm) excimer laser flash photolysis was investigated by ESR at 77 K. Beside radical products of cellulose generated and stabilized at low temperature, radicals in NMMO and cellulose/NMMO solutions were studied for the first time in those systems and attributed to nitroxide type radicals ∼CH2–NO•–CH2∼ and/or ∼CH2–NO•–CH3∼ at the first and methyl •CH3 and formyl •CHO radicals at the second step of the photo-induced reaction. Kinetic study of radicals revealed that formation and recombination rates of radical reaction depend on cellulose concentration in cellulose/NMMO solutions and additional ingredients, e.g., Fe(II) and propyl gallate. HPLC measurements showed that the concentrations of ring degradation products, e.g., aminoethanol and acetaldehyde, are determined by the composition of the cellulose/NMMO solution. Results based on HPLC are mainly maintained by ESR that supports the assumption concerning a radical initiated ring-opening of NMMO.
01 Jan 2007
TL;DR: In this article, the formation and recombination rates of radical reaction depend on cellulose concentration in cellulose/NMMO solutions and additional ingredients, e.g., Fe(II) and propyl gallate.
Abstract: Degradation processes of N-methylmorpholine-N-oxide monohydrate (NMMO), cellulose and cellulose/NMMO solutions were studied by high performance liquid chromatography (HPLC) and electron spin resonance (ESR) spectroscopy. Kinetics of radical accumulation processes under UV (λ = 248 nm) excimer laser flash photolysis was investigated by ESR at 77 K. Beside radical products of cellulose generated and stabilized at low temperature, radicals in NMMO and cellulose/NMMO solutions were studied for the first time in those systems and attributed to nitroxide type radicals ∼CH2–NO•–CH2∼ and/or ∼CH2–NO•–CH3∼ at the first and methyl •CH3 and formyl •CHO radicals at the second step of the photo-induced reaction. Kinetic study of radicals revealed that formation and recombination rates of radical reaction depend on cellulose concentration in cellulose/NMMO solutions and additional ingredients, e.g., Fe(II) and propyl gallate. HPLC measurements showed that the concentrations of ring degradation products, e.g., aminoethanol and acetaldehyde, are determined by the composition of the cellulose/NMMO solution. Results based on HPLC are mainly maintained by ESR that supports the assumption concerning a radical initiated ring-opening of NMMO.
TL;DR: In this paper, the application of synchrotron radiation x-ray microprobe to the study of Si impurities in plasma-induced molecular beam epitaxy grown Al0.32Ga0.68N was reported.
Abstract: In this study, the authors report on the application of synchrotron radiation x-ray microprobe to the study of Si impurities in plasma-induced molecular beam epitaxy grown Al0.32Ga0.68N. Elemental maps obtained by μ-x-ray fluorescence spectrometry show inhomogeneous distributions of Si, Al, and Ga on the micron scale. X-ray absorption near-edge structure spectra taken at the Si and Al K edges provided information about their local chemical environment and revealed the change of the spectral features as depending on the position compared to the sample surface and on the concentration of Si.
TL;DR: This work demonstrates the possibility of determining the AFM tip geometry and the tilt based on several different large structures and presents a new method for determining tip shape as it compares to other current methods.
TL;DR: In this paper, it is demonstrated that FTIRellipsometry is a suitable technique for monitoring the inhomogeneous residual stress inside SiC/Si heterostructures containing thin layers and their variation with during processing.
Abstract: The resonant frequencies and quality factors of MEMS and NEMS depend critically on the layer quality and the residual stress in the SiC/Si heterostructure. It is demonstrated, that FTIRellipsometry is a suitable technique for monitoring the inhomogeneous residual stress inside SiC/Si heterostructures containing thin layers and their variation with during processing.