28 research outputs found
Charge manipulation and imaging of the Mn acceptor state in GaAs by Cross-sectional Scanning Tunneling Microscopy
An individual Mn acceptor in GaAs is mapped by Cross-sectional Scanning
Tunneling Microscopy (X-STM) at room temperature and a strongly anisotropic
shape of the acceptor state is observed. An acceptor state manifests itself as
a cross-like feature which we attribute to a valence hole weakly bound to the
Mn ion forming the (Mn) complex. We propose that the observed
anisotropy of the Mn acceptor wave-function is due to the d-wave present in the
acceptor ground state.Comment: Proceedings of the SIMD-4 conference. Hawaii, USA (December 1-5,
2003
Magnetization reversal process and nonlinear magneto-impedance in Cu/NiFe and Nb/NiFe composite wires
The magnetization reversal of Cu/NiFe and Nb/NiFe composite wires carrying AC
current is studied. The frequency spectrum of a voltage induced in a pick-up
coil wound around the wire is analyzed. The frequency spectrum is shown to
consist of even harmonics within a wide range of AC current amplitudes and
longitudinal DC magnetic fields. The strong dependencies of the harmonic
amplitudes on the DC field are found. The results obtained may be of importance
for the design of weak magnetic field sensors.Comment: 8 pages, 4 figures, publishe
Imaging of the [Mn2+(3d5) + hole] complex in GaAs by Cross-sectional Scanning Tunneling Microscopy
We present results on the direct spatial mapping of the wave-function of a
hole bound to a Mn acceptor in GaAs. To investigate individual Mn dopants at
the atomic scale in both ionized and neutral configurations, we used a room
temperature cross-sectional scanning tunneling microscope (X-STM). We found
that in the neutral configuration manganese manifests itself as an anisotropic
cross-like feature. We attribute this feature to a hole weakly bound to the Mn
ion forming the [Mn2+(3d5) + hole] complex.Comment: 4 pages, 7 figure
Magnetic spin excitations in Mn doped GaAs : A model study
We provide a quantitative theoretical model study of the dynamical magnetic
properties of optimally annealed GaMnAs. This model has already
been shown to reproduce accurately the Curie temperatures for
GaMnAs. Here we show that the calculated spin stiffness are in
excellent agreement with those which were obtained from ab-initio based
studies. In addition, an overall good agreement is also found with available
experimental data. We have also evaluated the magnon density of states and the
typical density of states from which the "mobility edge", separating the
extended from localized magnon states, was determined. The power of the model
lies in its ability to be generalized for a broad class of diluted magnetic
semiconductor materials, thus it bridges the gap between first principle
calculations and model based studies.Comment: 5 pages, 5 figures, Text and some figures revised to match the
accepted versio
Multilayers for the lithography generation beyond EUVL
A potential candidate for the new generation lithography beyond EUV is La/B4C multilayer optics for λ = 6.x nm. Achieving the highest possible reflectance at near normal (1.5°) incidence requires substantial practical improvement of the structural perfection of the multilayers. Pure La/B4C multilayers suffer from the formation of relatively thick interlayer at the interfaces. We have found that N-ion and N2 gas treatment of the multilayer interfaces strongly reduces interlayer formation and therefore enhances the multilayer optical contrast which leading to increase of the reflectivity at 6.x nm. The wavelength dependence of the La/B4C and LaN/B4C multilayer reflectivity has been studied in order to investigate the spectral properties of multilayers near B-absorption edge. Calculation of the maximal reflectance for La/B4C and LaN/B4C reflectivity for various wavelengths (figure 1) predicts significant gain in reflectance near the B absorption edge. We will present the influence of N-ions treatment on reflectivity properties of La/B4C multilayers near the B absorption edge and discuss the effect on throughput of an entire lithography system
Wavelength selection for multilayer coatings for lithography generation beyond extreme ultraviolet
The spectral properties of LaN/B and LaNâB4C multilayer mirrors have been investigated in the 6.5 to 6.9 nm wavelength range, based on measured B and B4C optical constants. We show that the wavelength of optimal reflectance for boron-based optics is between 6.63 and 6.65 nm, depending on the boron chemical state. The wavelength of the maximum reflectance of the LaNâB4C multilayer system is confirmed experimentally. Calculations of the wavelength-integrated reflectance for perfect ten-multilayer-mirror stacks show that a B-based optical column can be optimized for a wavelength larger than 6.65 nm
Short period La/B and LaN/B multilayer mirrors for similar to 6.8 nm wavelength
In the first part of this article we experimentally show that contrast between the very thin layers of La and B enables close to theoretical reflectance. The reflectivity at 6.8 nm wavelength was measured from La/B multilayer mirrors with period thicknesses ranging from 3.5 to 7.2 nm at the appropriate angle for constructive interference. The difference between the measured reflectance and the reflectance calculated for a perfect multilayer structure decreases with increasing multilayer period. The reflectance of the multilayer with the largest period approaches the theoretical value, showing that the optical contrast between the very thin layers of these structures allows to experimentally access close to theoretical reflectance. In the second part of the article we discuss the structure of La/B and LaN/B multilayers. This set of multilayers is probed by hard X-rays (lambda = 0.154 nm) and EUV radiation (lambda = 6.8 nm). The structure is reconstructed based on a simultaneous fit of the grazing incidence hard X-ray reflectivity and the EUV reflectivity curves. The reflectivity analysis of the La/B and LaN/B multilayer mirrors shows that the lower reflectance of La/B mirrors compared to LaN/B mirrors can be explained by the presence of 5% of La atoms in the B layer and 63% of B in La layer. After multi-parametrical optimization of the LaN/B system, including the nitridation of La, the highest near normal incidence reflectivity of 57.3% at 6.6 nm wavelength has been measured from a multilayer mirror, containing 175 bi-layers. This is the highest value reported so far. (C) 2013 Optical Society of Americ
Wavelength selection for multilayer coatings for the lithography generation beyond EUVL
The spectral properties of LaN/B and LaN/B4C multilayer mirrors have been investigated in the 6.5-6.9 nm wavelength range, based on measured B and B4C optical constants. We show that the wavelength of optimal single mirror reflectance for boron based optics is between 6.63 and 6.65 nm, depending on the boron chemical state. The wavelength of the maximum reflectance of the LaN/B4C multilayer system is confirmed experimentally. Calculations of the wavelengthintegrated reflectance for ideal 10-multilayer-mirror stacks show that a B-based optical column can be optimized for a wavelength larger than 6.65 nm