On the basis of high resolution STM images and DFT modeling, we have resolved low- high-coverage structures methylthiolate (CH(3)S) self-assembled on Au(111) surface. The key new finding is that building block all these has same stoichiometry two thiolate species joined by a gold adatom. self-arrangement methylthiolate-adatom complexes surface depends critically their stereochemical properties. Variations latter can produce local ordering adatom with either (3 x 4) or 4 square root(3))...

The surface plasmon resonance tracking over metal surfaces is a well-established, commercially available, biochemical quantification tool primarily applied in research. utilization of such is, however, constrained to highly specialized industries, capable justifying the human and instrumental resource investments required by characterization method. We have proposed expand field application this biosensing approach redesigning method through integration miniaturization within semiconductor...

Modern miniaturization and the digitalization of characterization instruments greatly facilitate diffusion technological advances in new fields generate innovative applications. The concept a portable, inexpensive semi-automated biosensing platform, or lab-on-a-chip, is vision shared by many researchers venture industries. Under this scope, we present semiconductor monolithic integration approach to conduct surface plasmon resonance studies. This technology already commonly used for...

Photocorrosion of semiconductors is strongly sensitive to the presence surface states, and it could be influenced by electrically charged molecules immobilized near semiconductor/electrolyte interface. The underlying mechanism related band bending semiconductor structure associated distribution excited electrons holes. authors have employed photoluminescence GaAs/AlGaAs quantum heterostructures for monitoring in situ photocorrosion effect, demonstrating detection nongrowing Legionella...

Self-assembled monolayers (SAMs) of various thiols have shown the potential to protect freshly fabricated or chemically cleaned GaAs surfaces from oxidization, adsorption foreign atoms, and∕or surface defect formation. We employed an attenuated total reflection Fourier-transform infrared spectroscopic technique investigate process formation long-chain thiols, comprising ten more methylene chains, on (001) GaAs. A strong (IR) signal was measured for all investigated GaAs-thiol interfaces....

Epitaxial (100) CdTe films were grown on the GaAs surface by pulsed laser evaporation. The growth was achieved substrates held at 260 °C and under a pressure of about 8×10−8 Torr. High-energy electron diffraction, x-ray UV reflectivity studies have shown that epilayers high crystalline quality obtained. morphology thicker than 0.4 μm approached atomic smoothness. No incorporated impurities, including oxygen carbon, found Auger spectroscopy in studied.

Observed properties of thiol self-assembled monolayers (SAMs) on GaAs (001) surfaces can be explained by the presence surface reconstructions, but their exact form is generally unknown. We propose a new approach to modeling SAM-surface interface based using alkanethiol dense packing structures as starting point and adjusting reconstruction accommodate them. Obtained in such way, model SAMs adsorb along trenches [110] direction exhibit 19 degrees tilt +/- 45 twist angles, agreement with...

Digital photocorrosion (DIP) of GaAs/AlGaAs nanoheterostructures is an attractive method for detecting surface‐immobilized electrically charged biomolecules such as bacteria. The process normally carried out in ammonia‐ or phosphate‐buffered saline and monitored situ to reveal photoluminescence (PL) intensity maximum (PL max ) when the front crosses GaAs‐AlGaAs interface. temporal position PL plotted a function concentration allows calibration detection unknown concentrations Successive...

Laser annealing of InAs/GaAs quantum-dot (QD) microstructures has been investigated for selective area tuning their electronic shell structure. Extensive blueshifts the QD excited states were observed following 20–40 s laser irradiation. In most extreme case, we able to shift position ground state transition by 298 meV, i.e., spectral region where photoluminescence signal originates from as-grown InAs wetting layer. A reduction ∼50 8 meV full width at half maximum PL peak corresponding this...

Using alkanethiol dense packing as a starting point, we have found six prototypical structures commensurate with the (3 × 2√3) supercell of Au (111) surface. Five are not compatible flat surface conditions but can be fitted to reconstructed Combined density functional theory calculations and simulations grazing incidence X-ray diffraction maps scanning tunneling microscopy images, this allowed us refine assess recently proposed models c(4 2) self-assembled monolayers involving...

Adsorption mechanisms of hydrogen sulfide and alkanethiols on GaAs (001) surfaces prepared in a vacuum were studied using first principles calculations. The need for physisorbed precursor was confirmed based energetic arguments molecular dynamics simulations the transition from physisorption to chemisorption state. preference S−Ga bond formation found, resulting weak non-dissociative state formed by overlap sulfur lone pair orbital with an empty Ga dangling bond. Physisorption energies...

We report on a method of rapid conversion hydrophobic to hydrophilic state an Si (0 0 1) surface irradiated with relatively low number pulses excimer laser. Hydrophilic 1), characterized by the contact angle (CA) near 15°, is fabricated following irradiation either KrF or ArF lasers samples (CA ∼ 75°) immersed in 0.01% H2O2/H2O solution. The chemical and structural analysis carried x-ray photoelectron spectroscopy atomic force microscopy measurements confirmed formation OH-terminated no...

We report on the formation kinetics of mixed self-assembled monolayers (SAMs) comprising 16-mercaptohexadecanoic acid (MHDA) and 11-mercapto-1-undecanol (MUDO) thiols GaAs(100) substrates. These compounds were selected for their potential in constructing highly selective efficient architectures biosensing applications. The molecular composition quality one-compound SAMs determined by Fourier transform infrared absorption spectroscopy measurements. enhanced-quality was investigated as a...

We have measured resonant Raman scattering and photoluminescence from thin (001) CdTe films grown by pulsed laser evaporation epitaxy on GaAs. LO phonon overtones up to sixth order are observed under outgoing resonance conditions near the ${E}_{0}+{\ensuremath{\Delta}}_{0}$ (conduction ${\ensuremath{\Gamma}}_{6}$ spin-orbit split-off valence ${\ensuremath{\Gamma}}_{7}$ bands) gap. discuss mechanisms for overtones. Photoluminescence gap is seen at 80 K, first time without help of carrier...

This paper investigates a high sensitive piezoelectric sensor in Gallium Arsenide (GaAs) crystal for biological molecules detection liquid environment. The lateral field excitation was used to generate bulk acoustic waves (BAW) through (001) GaAs membranes. crystallographic plane and the electric orientation were chosen obtain highest electromechanical coupling coefficient shear waves. presents interesting alternative quartz concerning resonant biosensors thanks its piezoelectric,...