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We report the characterization of the formation of an imidazolium bridging unit in the synthesis of titania-based nanoparticle networks. By using a combination of different analytical techniques, such as ellipsometry or atomic force microscopy, we are able to show that the nanoparticles are indeed covalently bound to the substrate. By oxidation of the organic linker after monolayer formation, covalently bound, fully inorganic nanoparticle monolayer structures are obtained. Furthermore, the layer-by-layer deposition method is extended to the synthesis of thin films containing, in a controlled manner and at the same time, silica and titania nanoparticles.

Machinelike operations are common functions in biological systems, and substantial recent research efforts are directed to mimic such processes at the molecular or nanoscale dimensions. The present Feature Article presents three complementary approachscate the present es to design machinelike operations: by the signal-triggered mechanical shuttling of molecular components; by the signal-triggering of chemical processes on surfaces, resulting in mechanical motion of micro/nanoscale objects; and by the fuel-triggered motility of biomolecule-metal nanowire hybrid systems. The shuttling of molecular components on molecular wires assembled on surfaces in semirotaxane configurations using electrical or optical triggering signals is described. The control of the hydrophilic/hydrophobic surface properties through molecular shuttling or by molecular bending/stretching processes is presented. Stress generated on microelements, such as cantilevers, results in the mechanical deflection of the cantilever. The deposition of a redox-active polyaniline film on a cantilever allows the reversible electrochemically induced deflection and retraction of the cantilever by the electrochemical oxidation or reduction of the polymer film, respectively. A micro-robot consisting of the polypyrrole (PPy) polymer deposited on a multi-addressable configuration of electrodes is described. Au magnetic core/shell nanoparticles are incorporated into a polyaniline film, and the conductivity of the composite polymer is controlled by an external magnet. Finally, the synthesis of a hybrid nanostructure consisting of two actin filaments tethered to the two ends of a Au nanowire is described. The adenosine triphosphate (ATP)-fueled motility of the hybrid nanostructure on a myosin monolayer associated with a solid support is demonstrated.

Biomolecule–nanoparticle (NP) [or quantum-dot (QD)] hybrid systems combine the recognition and biocatalytic properties of biomolecules with the unique electronic, optical, and catalytic features of NPs and yield composite materials with new functionalities. The biomolecule–NP hybrid systems allow the development of new biosensors, the synthesis of metallic nanowires, and the fabrication of nanostructured patterns of metallic or magnetic NPs on surfaces. These advances in nanobiotechnology are exemplified by the development of amperometric glucose sensors by the electrical contacting of redox enzymes by means of AuNPs, and the design of an optical glucose sensor by the biocatalytic growth of AuNPs. The biocatalytic growth of metallic NPs is used to fabricate Au and Ag nanowires on surfaces. The fluorescence properties of semiconductor QDs are used to develop competitive maltose biosensors and to probe the biocatalytic functions of proteases. Similarly, semiconductor NPs, associated with electrodes, are used to photoactivate bioelectrocatalytic cascades while generating photocurrents.

Hg(2+) ions are bound to a 1,4-benzenedimethanethiol (BDMT) monolayer assembled on a Au electrode. Electrochemical reduction of the Hg(2+)-BDMT monolayer to Hg(+)-BDMT (at E degrees =0.48 V) and subsequently to Hg(0)-BDMT (at E degrees =0.2 V) proceeds with electron-transfer rate constants of 8 and 11 s(-1), respectively. The Hg(0) atoms cluster into aggregates that exhibit dimensions of 30 nm to 2 microm, within a time interval of minutes. Electrochemical oxidation of the nanoclusters to Hg(+) and further oxidation to Hg(2+) ions proceeds with electron-transfer rate constants corresponding to 9 and 43 s(-1), respectively, and the redistribution of Hg(2+) on the thiolated monolayer occurs within approximately 15 s. The reduction of the Hg(2+) ions to the Hg(0) nanoclusters and their reverse electrochemical oxidation proceed without the dissolution of mercury species to the electrolyte, implying high affinities of Hg(2+), Hg(+), and Hg(0) to the thiolated monolayer. The electrochemical transformation of the Hg(2+)-thiolated monolayer to the Hg(0)-nanocluster-functionalized monolayer is characterized by electrochemical means, surface plasmon resonance (SPR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), and contact-angle measurements. The Hg(0)-nanocluster-modified surface reveals enhanced hydrophobicity (contact angle 76 degrees ) as compared to the Hg(2+)-thiolated monolayer (contact angle 57 degrees ). The hydrophobic properties of the Hg(0)-nanocluster-modified electrode are further supported by force measurements employing a hydrophobically modified AFM tip.

The charge transport properties in composites consisting of pyrene sulfonic acid-functionalized single-walled carbon nanotubes embedded in polyaniline, PAn/SWCNTs, and polystyrene sulfonate-doped PAn, PAn/PSS, are compared in thin-film and microrods configurations. The PAn/SWCNTs and PAn/PSS microrods were prepared by the electropolymerization of the respective components in porous alumina membranes coated with a conductive gold support, followed by the dissolution of the membrane template. The charge transport upon the oxidation of the PAn/SWCNTs planar film or microrods structures is ca. 3.5–4.0-fold faster than upon the oxidation of the PAn/PSS planar film or microrods structures, respectively. The faster charge transport in the PAn/SWCNTs films and microrods is used to enhance the mediated bioelectrocatalyzed oxidation of glucose in the presence of glucose oxidase (GOx). The bioelectrocatalyzed oxidation of glucose in the presence of the PAn/SWCNTs in the planar film and microrods structures is ca. 2-fold and up to 6-fold (depending on the potential) enhanced as compared to the respective PAn/PSS configurations.

Composite materials consisting of polyaniline/poly(4-styrene-sulfonate) (PAn/PSS) or polyaniline/Au nanoparticles capped with 2-mercaptoethane sulfonic acid (PAn/Au-NPs) are prepared in the form of...

We present a new approach for the generation of metallic nano dots. In contrast to conventional bottom up or top down processes, this novel technique is based on a subtractive self organization process relying on material decomposition induced by focused ion beam (FIB) exposure. The dot formation is discussed in terms of selective etching due to the local energy injection by the ions and further agglomeration. Finally, the formation of ordered arrays of dots is demonstrated by a site control technique relying on preformed craters and irradiation mediated migration.

The impact of 50 keV focused Ga þ ion bombardment on semi-insulating GaAs has been investigated at various ion fluences in the range of 6.25 · 10 10 –1.25 · 10 17 ions/cm 2 . As a result, the formation of spherical calotte shaped dots consisting of nearly pure gallium has been observed. The diameter of the calottes is in the range of 100 nm to more than 1 lm with an almost constant aspect ratio of about 0.4. The Ga dot formation promotes decomposition of the Ga-rich surface far below temperatures that have been reported for the thermal decomposition of undisturbed GaAs. The material decomposition occurs exclusively in the implanted regions, leading to micelle like structures on the irradiated surface. In this work, we present an experimental study of the morphological, chemical and electrical evolution of the GaAs surface under focused ion beam exposure by in situ FIB-secondary electron microscopy combined with atomic force microscopy, Auger electron spectroscopy, optical microscopy, and electrical measurements.

We present a fast and straightforward method for the cross-sectional analysis of self-assembled InAs quantum dots using atomic force microscopy. The new approach needs a minimum amount of time and sample preparation (cleaving and, if necessary, etching with a solution of hydroxylamine/hydrogen-peroxide) to obtain the cross-sectional dot density and information on the degree of stacking, which are important parameters in the production of self-assembled quantum dot devices, and provides the means for fast cross-sectional wafer mapping.

Recently nanoparticles ionic networks were reported in the frame of the remarkable development of new inorganic-organic hybrid materials based on nanoparticles assembly. In this article a layer-by-layer deposition method for the formation of imidazolium-based assemblies of photocatalytic titania nanoparticles is presented. This provides a new route for the controlled processing of this promising class of materials.

Scanning probe methods like atomic force microscopy (AFM) and related techniques are promising candidates for morphological, physical, and chemical characterization of surfaces on the sub-micrometer scale. In order to evaluate the analytical potential of tapping mode AFM for obtaining material specific information on surface structures along with topography, we have studied the influence of various experimental parameters on height and phase contrast using self-assembled monolayers (SAMs) as well defined model systems. The organic films were deposited onto silicon substrates starting from alkyltrichlorosilanes with methyl-, ester-, and hydroxyl-end groups, respectively. As a result it was found that reproducibility suffers from the fact that even small changes in parameters determining the force interaction between tip and sample can lead to pronounced changes in image contrast. Nevertheless it has been possible to identify comparatively stable regions for the imaging parameters allowing to distinguish different sample systems by their specific pattern of height and phase contrasts, which can be seen as a valuable analytical contribution towards sub-micrometer chemical imaging with scanning probe microscopy.

AFM imaging of the adsorption of self-assembled octadecylsiloxane (ODS) monolayers has been utilized for probing surface properties of silicon wafers. It has been found that both growth rate of the organic films and island size of sub-monolayer films are influenced by the doping level of the wafers as well as by the surface finishing step during wafer production. Generally, higher doping levels led to lower adsorption rates and smaller islands. Variation of the sample pretreatment used for surface finishing of similarly doped wafers led only to significant changes of the island size, but not of the surface coverage. The results presented open up a valuable perspective for characterizing the surface homogeneity of silicon wafers which is an important parameter for monitoring-wafers in semiconductor industry.

We describe a new method for 3 dimensional nanostructuring on silicon surfaces using self-assembled monolayers. Partial multilayers were formed by repeated deposition of trichlorosilylheptadecanoic acid methyl ester (TSHEME) and subsequent reduction to yield a hydroxylic surface. These structures were afterwards oxidised using UV/ozone, yielding silicon oxide features. In this way both organic multilayered structures as well as ones comprised of silicon oxide have been produced with precise control of the height and invariant lateral shape of these structures. We have tried to apply samples prepared in this fashion to the calibration of AFM-scanners in vertical direction. Due to height artefacts caused by the tip-sample interaction a general calibration is not possible on the molecular scale. However, the structures produced can be used as model systems for the investigation of various sources of height artefacts and also for calibration purposes as long as samples with similar chemical and mechanical properties are to be investigated.

We present GaN-based high electron mobility transistors (HEMTs) with a 2-nm-thin InAlN/AlN barrier capped with highly doped n(++) GaN. Selective etching of the cap layer results in a well-controllable ultrathin barrier enhancement-mode device with a threshold voltage of +0.7 V. The n(++) GaN layer provides a 290-Omega/square sheet resistance in the HEMT access region and eliminates current dispersion measured by pulsed IV without requiring additional surface passivation. Devices with a gate length of 0.5-mu m exhibit maximum drain current of 800 mA/mm, maximum transconductance of 400 mS/mm, and current cutoff frequency f(T) of 33.7 GHz. In addition, we demonstrate depletion-mode devices on the same wafer, opening up perspectives for reproducible high-performance InAlN-based digital integrated circuits.

The fabrication of bottom-up nanostructures is a crucial step for the advancement of nanotechnology. Dip-pen nanolithography has started off as a method for the transfer of small organic molecules and has matured over the years to one of the most versatile patterning techniques available in the nanoscale. Three-dimensional structures made from organic or inorganic materials on a large variety of different substrates and length scales have been fabricated. This review highlights the techniques used for the fabrication of these structures together with their practical applications. Furthermore, the physical mechanisms involved in the dip-pen process are discussed by summarizing the experimental and theoretical results obtained so far.

In this work, the physical processes leading to contrast in scanning capacitance microscopy (SCM) are investigated both experimentally and theoretically. Using a p-type epitaxial doping staircase on silicon, we show that a monotonic dependence of the SCM signal on the doping level is only obtained, if the tip bias is adjusted in a way that the sample is either in accumulation or depletion. In the transition region, the SCM signal is nonmonotonic as a function of doping and depends on the bias. Therefore, any doping concentration can yield a maximum SCM signal size. We also show that this behavior is in agreement with the conventional model of a metal-oxide-semiconductor junction.

Design considerations and performance of n(++) GaN/InAlN/AlN/GaN normally off high-electron mobility transistors (HEMTs) are analyzed. Selective and damage-free dry etching of the gate recess through the GaN cap down to a 1-nm-thick InAlN barrier secures positive threshold voltage, while the thickness and the doping of the GaN cap influence the HEMT direct current and microwave performance. The cap doping density was suggested to be 2 x 10(20) cm(-3). To screen the channel from the surface traps, the needed cap thickness was estimated to be only 6 nm. Design is proved by an experiment showing a constant value of the HEMT dynamical access resistance, while a single-pulse experiment indicated almost collapse-free performance. On the other hand, it is found that the n(++) GaN cap does not contribute to the HEMT drain current conduction, nor does it provide a path for the OFF-state breakdown. HEMTs with a gate length of 0.25 mu m and a 4-mu m source-to-drain distance show a drain-to-source current of 0.8 A/mm, a transconductance of 440 mS/mm, a threshold voltage of similar to 0.4 V, and a cutoff frequency of 50 GHz. A thin and highly doped GaN cap is also found to be suitable for the processing of normally on HEMTs by adopting the nonrecessed gate separated from the cap by insulation.

We correlate dc maximal drain current I DSmax , pulsed output characteristics, rf small-signal and breakdown performance of normally-off InAlN/GaN HEMTs with varied gate-to-drain distance d GD . It is found that parasitic lag effects which are related to the possible surface states are not appearing at longer d GD . On the other hand compromise need to be found between the improved gate performance and impaired I DSmax and f T as the d GD is increased. The leakage current of the 0.5 µm-long gate may be reduced by up-to three orders of magnitude, down to µA/mm at −20 V bias if d GD increases from 3 to 15 µm. On the other hand I DSmax and f T drop by about one third of the original value (from about 0.6 A/mm and 34 GHz down to 0.4 A/mm and 21 GHz, respectively) if d GD changes.

Dip-pen nanolithography (DPN) is a powerful method to pattern nanostructures on surfaces by the controlled delivery of an "ink" coating the tip of an atomic force microscope upon scanning and contacting with surfaces. The growing interest in the use of nanoparticles as structural and functional elements for the fabrication of nanodevices suggests that the DPN-stimulated patterning of nanoparticles on surfaces might be a useful technique to assemble hierarchical architectures of nanoparticles that could pave methodologies for functional nanocircuits or nanodevices. This Review presents different methodologies for the nanolithographic patterning of metallic, semiconductor, and metal oxide nanostructures on surfaces. The mechanisms involved in the formation of the nanostructures are discussed and the effects that control the dimensions of the resulting patterns are reviewed. The possible applications of the nanostructures are also addressed.

Submonolayers of octadecylsiloxane (ODS) were prepared by adsorption from dilute solutions of octadecyltrichlorosilane (OTS) onto a series of different substrates: mica, native silicon (Si/SiO2), and mica coated with a defined number nSiO of SiO2 monolayers (nSiO = 1, 2, 4, 6). Atomic force microscopy (AFM) was used to investigate the adsorption rate and the submonolayer island morphology as a function of the substrate composition. Two types of substrate effects were observedfirst, an abrupt change of the shape, size, and height distribution of the submonolayer islands between mica and SiO2-coated mica or silicon substrates, and second, an exponential decrease of the adsorption rate with nSiO up to a thickness of about 6 SiO2 monolayers. The first effect is independent of the SiO2 film thickness and the nature of the underlying substrate (mica or Si) and is therefore believed to arise from the different surface concentrations of OH groups on mica and SiO2 surfaces. The adsorption rate decrease with nSiO,...

We present a novel approach for the reversible switching of the emission wavelength of a quantum cascade laser (QCL) using a halochromic cladding. An air-waveguide laser ridge is coated with a thin layer of polyacrylic acid. This cladding introduces losses corresponding to the absorption spectrum of the polymer. By changing the state of the polymer, the absorption spectrum and losses change, inducing a shift of 7 cm(-1) in the emission wavelength. This change is induced by exposure to acidic or alkaline vapors under ambient conditions and is fully reversible. Such lasers can be used as multi-color light source and as sensor for atmospheric pH.

We present a novel method for the reversible switching between different emission wavelengths for a grating-free mid-IR QCL utilizing the absorbance changes of a pH-responsive cladding under ambient conditions.

A C18 monolayer-functionalized Si surface is electrochemically patterned to yield a carboxylic acid-terminated pattern. Tyramine is covalently linked to the pattern to yield an encoded nanostructure for the enzyme tyrosinase. The biocatalytic oxidation of the tyramine residues yields catechol moieties that control the assembly of boronic acid-functionalized Au nanoparticles (NPs) or magnetic NPs. The different NPs are linked to the patterns by the formation of complexes between the boronic acid residues or Fe3+ ions and the catechol ligands.

Circular DNA is used as a template for the amplified detection of M13 phage ssDNA by a rolling circle amplification (RCA) process that synthesizes DNAzyme chains, thus enabling the colorimetric or chemiluminescent detection of the analyte.

Biomolecule-nanoparticle (NP) [or quantum-dot (QD)] hybrid systems combine the recognition and biocatalytic properties of biomolecules with the unique electronic, optical, and catalytic features of NPs and yield composite materials with new functionalities. The biomolecule-NP hybrid systems allow the development of new biosensors, the synthesis of metallic nanowires, and the fabrication of nanostructured patterns of metallic or magnetic NPs on surfaces. These advances in nanobiotechnology are exemplified by the development of amperometric glucose sensors by the electrical contacting of redox enzymes by means of AuNPs, and the design of an optical glucose sensor by the biocatalytic growth of AuNPs. The biocatalytic growth of metallic NPs is used to fabricate Au and Ag nanowires on surfaces. The fluorescence properties of semiconductor QDs are used to develop competitive maltose biosensors and to probe the biocatalytic functions of proteases. Similarly, semiconductor NPs, associated with electrodes, are used to photoactivate bioelectrocatalytic cascades while generating photocurrents.

The rupture forces between an aptamer (1)-functionalized AFM tip and a thrombin-modified Au surface are analyzed. The rupture force for a single aptamer/thrombin complex is determined as approximately 4.45 pN. The analysis of the system reveals that the rupture forces correspond to the melting of the G-quadruplex structure of the aptamer bound to the thrombin. This melting of the G-quadruplex leads to the dissociation of the aptamer/thrombin complex.

The electroswitchable and the biocatalytic/electrochemical switchable interfacial properties of a Ag(+)-biphenyldithiol (BPDT) monolayer associated with a Au surface are described. Upon the application of a potential corresponding to -0.2 V the Ag(+)-BPDT is reduced to the Ag(0)-BPDT interface, and silver nanoclusters are generated on the interface. The application of a potential that corresponds to 0.2 V reoxidizes the monolayer to the Ag(+)-BPDT monolayer. The reversible electrochemical transformation of the Ag(+)-BPDT monolayer and of the Ag(0)-BPDT surface was followed by electrochemical means and surface plasmon resonance spectroscopy (SPR). The SPR experiments enabled us to follow the kinetics of nanoclustering of Ag(0) on the surface. The hydrophobic/hydrophilic properties of the surface are controlled by the electrochemically induced transformation of the interface between the Ag(+)-BPDT and Ag(0)-BPDT states. The Ag(0)-BPDT monolayer reveals enhanced hydrophilicity. The hydrophobic/hydrophilic properties of the interface were probed by contact angle measurements and force interactions with a hydrophobically-functionalized AFM tip. The Ag(0)-BPDT interface was also biocatalytically generated using alkaline phosphatase, AlkPh, and p-aminophenyl phosphate as substrate. The biocatalytically generated p-aminophenol reduces Ag(+) ions associated with the surface to Ag(0) nanoclusters. This enables the cyclic biocatalytic/electrochemical control of the surface properties of the modified electrode.

In our previous work we showed that a reproducible monotonic relation between Scanning Capacitance Microscopy (SCM) signal and the sample doping is obtained under appropriate SCM operating conditions. In this work, we quantitatively determine the two‐dimensional carrier distribution of an n‐type ion‐implanted collector region of an industrial transistor sample. As the structures were large enough so that tip geometry effects could be neglected, the SCM data were converted into a two‐dimensional doping distribution via a simple lookup table, which was generated from a one‐dimensional doping profile measured on a reference wafer. In case the depth distribution of carriers is unknown, we show that the lookup table can also be calculated and a calibration can be carried out using e.g. the substrate doping as reference point.

Magnetic nanoparticles consisting of undecanoate-capped magnetite (average diameter approximately 4.5 nm; saturated magnetization, M(s), 38.5 emu g(-1)) are used to control and switch the hydrophobic or hydrophilic properties of the electrode surface. A two-phase system consisting of an aqueous buffer solution and a toluene phase that includes the suspended capped magnetic nanoparticles is used to control the interfacial properties of the electrode surface. The magnetic attraction of the functionalized particles to the electrode by means of an external magnet yields a hydrophobic interface that acts as an insulating layer, prohibiting interfacial electron transfer. The retraction of the magnetic particles from the electrode to the upper toluene phase by means of the external magnet generates a hydrophilic electrode that reveals effective interfacial electron transfer. The electron-transfer resistance and double-layer capacitance of the electrode surface upon the attraction and retraction of the functionalized magnetic particles to and from the electrode, respectively, by means of the external magnet were probed by Faradaic impedance spectroscopy (R(et) = 170 Omega and C(dl) = 40 microF sm(-2) in the hydrophilic state of the electrode and R(et) = 22 k Omega and C(dl) = 0.5 microF sm(-2) in the hydrophobic state of the interface). The magnetoswitchable control of the interface enables magnetic switching of the bioelectrocatalytic oxidation of glucose in the presence of glucose oxidase and ferrocene dicarboxylic acid to "ON" and "OFF" states.

A method for tuning the emission of a midinfrared quantum cascade laser using ultraviolet light is presented. The method uses a quantum cascade laser where a photochromic material is deposited as the top waveguide cladding. Changing the state of the cladding causes variations in the absorbance of the cladding. Wavelength dependent changes in the waveguide losses occur, forcing the laser to emit at a wavelength correlated with an absorbance minimum of the cladding. A blueshift by about 6 cm−1 was obtained at room temperature under UV irradiation which was fully reversed by exposure to visible light or room temperature relaxation.

We report on an annealing-induced “gate sinking” effect in a 2-nm-thin In0.17Al0.83N/AlN barrier high electron mobility transistor with Ir gate. Investigations by transmission electron microscopy linked the effect to an oxygen containing interlayer between the gate metal and the InAlN layer and revealed diffusion of oxygen into iridium during annealing. Below 700 °C the diffusion is inhomogeneous and seems to occur along grain boundaries, which is consistent with the capacitance-voltage analysis. Annealing at 700 °C increased the gate capacitance over a factor 2, shifted the threshold voltage from +0.3 to +1 V and increased the transconductance from 400 to 640 mS/mm.

We present an approach for the generation of uniform metallic nanodots which, in contrast to conventional bottom up or top down processes, is based on a subtractive self-organization process relying on material decomposition induced by focused ion beam exposure. Nearly pure gallium dots were fabricated on GaAs (100) using a 50 keV Ga focused ion beam at normal incidence and a subsequent rapid thermal annealing. A dose of 2.5×1016 ions/cm2 can be considered as a threshold dose for the development of dots on GaAs (100). The diameters of these dots range from 120 to 850 nm with an aspect ratio of about 0.4 and a dot density of up to 7.23×107/cm2. Two-dimensional ordered arrays of embedded as well as freestanding Ga dots were fabricated by a site control technique relying on pre-patterned holes and an irradiation mediated migration and agglomeration.

We present an approach for the generation of metallic Ga dots and In nano-crystallites which, in contrast to conventional bottom-up or top-down processes, is based on a subtractive self-organization process relying on material decomposition induced by focused ion beam exposure. The diameters of the Ga dots range from 120to850nm with an aspect ratio of about 0.4 at a dot density of up to 7×107∕cm2. Two-dimensional ordered arrays of freestanding dots were fabricated by a site control technique relying on prepatterned holes and an irradiation mediated migration and agglomeration. By the analogous technique we generated indium nanocrystallites on the (100) InAs surface with sizes ranging from about 50nm to a few microns obviously due to a preferential loss of arsenic atoms during Ga+ focused ion beam irradiation. The influence of the ion dose, the beam energy, and the dose rate on the surface evolution was investigated by atomic force microscopy, scanning electron microscopy, Auger electron spectroscopy, and ...

Focused ion beam techniques are among the most important tools for the nanostructuring of surfaces. As the physical phenomena during milling are not fully understood yet, we have applied the phase imaging capabilities of tapping mode atomic force microscopy to the investigation of surface amorphization, sputtering, and redeposition caused by focused ion beam irradiation. We have performed single spot as well as large area (20×20 μm2) irradiation of silicon (100) wafers. We describe the localized formation of amorphous and electrostatically charged domains, which do not correlate to topographic features.

Focused ion beam (FIB) technology has been demonstrated to be a powerful tool in microfabrication, primarily for semiconductor related processing. The migration of the critical dimensions of devices toward the nanometer regime necessitates the knowledge of fundamental milling process mechanisms to gain full use of the opportunities offered by the focused ion beam technique. We have investigated the influence of declining feature sizes on the focused ion beam response of GaAs. Based on our experimental results, a sputter yield promoting the self-focusing effect combined with a sputter rate increase at oblique angles, an opposing dose deficiency effect, and material redeposition for milling aspect ratios >1 are identified to be responsible for the complex sputter response of GaAs. In addition, the observed preferential etching of arsenic results in local precipitates of mobile Ga-rich residues influencing the fundamental characteristics of FIB patterning, like sputter yield, crater bottom flatness, and ripp...

Using Si samples with 400-nm-wide alternately high and low doped p-type layers on p-type substrate, we investigate the dependence of the scanning capacitance microscope (SCM) signal amplitude as a function of oxide thickness and dopant concentration. The oxide layers were created by a standard industrial high temperature oxidation process. Together with the implementation of the newly developed conductive diamond tips, good and quantitatively reproducible contrast for differently doped domains is obtained on all samples. A comparison with conventional metal-oxide-semiconductor theory shows good correlation for the decrease of the capacitance signal with increasing insulator thickness and increasing dopant concentration. Furthermore, geometry effects, such as the influence of the domain width on the SCM signal, are discussed.

We present a novel method for the thermal tuning of a grating-free mid-IR QCLs utilizing the absorbance changes of a thermochromic cladding. Both higher tuning coefficients as well as thermostable emission are achievable.

We present a novel method for the light-induced tuning of a grating-free mid-IR QCL utilizing the absorbance changes of a photochromic cladding. This photosensitization allowed for reversible shifts in the emission wavelength of 5 cm−1.