34 research outputs found
Synthesis of Graphene on Gold
Here we report chemical vapor deposition of graphene on gold surface at
ambient pressure. We studied effects of the growth temperature, pressure and
cooling process on the grown graphene layers. The Raman spectroscopy of the
samples reveals the essential properties of the graphene grown on gold surface.
In order to characterize the electrical properties of the grown graphene
layers, we have transferred them on insulating substrates and fabricated field
effect transistors. Owing to distinctive properties of gold, the ability to
grow graphene layers on gold surface could open new applications of graphene in
electrochemistry and spectroscopy.Comment: 8 pages, 4 figure
RETRATO EN EL PATIO [Material gráfico]
INCLUIDAS EN EL PEQUEÑO ÁLBUM FOTOGRÁFICO FAMILIAR DE LA COLECCIÓN LUIS SUÁREZ GALVÁNCopia digital. Madrid : Ministerio de Educación, Cultura y Deporte. Subdirección General de Coordinación Bibliotecaria, 201
Gibbs Free Energy Assisted Passivation Layers
Reduction of surface leakage is a major challenge in most photodetectors that requires the elimination of surface oxides on etched mesas during passivation. Engineering the passivation requires close attention to chemical reactions that take place at the interface during the process. In particular, removal of surface oxides may be controlled via Gibbs reactivity. We have compared electrical performance of type-II superlattice photodetectors, designed for MWIR operation, passivated by different passivation techniques. We have used ALD deposited Al2O3, HfO2, TiO2, ZnO, PECVD deposited SiO2, Si3N4 and sulphur containing octadecanethiol (ODT) self-assembled monolayers (SAM) passivation layers on InAs/GaSb p-i-n superlattice photodetectors with cutoff wavelength at 5.1 mu m. In this work, we have compared the result of different passivation techniques which are done under same conditions, same epitaxial structure and same fabrication processes. We have found that ALD deposited passivation is directly related to the Gibbs free energy of the passivation material. Gibbs free energies of the passivation layer can directly be compared with native surface oxides to check the effectiveness of the passivation layer before the experimental study.Wo
Low dark current N structure superlattice MWIR photodetectors
Commercially available read out integrated circuits (ROICs) require the FPA to have high dynamic resistance area product at zero bias (R(0)A) which is directly related to dark current of the detector. Dark current arises from bulk and surface contributions. Recent band structure engineering studies significantly suppressed the bulk contribution of the type-II superlattice infrared photodetectors (N structure, M structure, W structure). In this letter, we will present improved dark current results for unipolar barrier complex supercell superlattice system which is called as "N structure". The unique electronic band structure of the N structure increases electron-hole overlap under bias, significantly. N structure aims to improve absorption by manipulating electron and hole wavefunctions that are spatially separated in T2SLs, increasing the absorption while decreasing the dark current. In order to engineer the wavefunctions, we introduce a thin AlSb layer between InAs and GaSb layers in the growth direction which also acts as a unipolar electron barrier. Despite the difficulty of perfect lattice matching of InAs and AlSb, such a design is expected to reduce dark current. Experiments were carried out on Single pixel with mesa sizes of 100 x 100 - 700 x 700 mu m photodiodes. Temperature dependent dark current with corresponding R(0)A resistance values are reported
Graphene-Quantum Dot Hybrid Optoelectronics at Visible Wavelengths
With exceptional
electronic and gate-tunable optical properties,
graphene provides new possibilities for active nanophotonic devices.
Requirements of very large carrier density modulation, however, limit
the operation of graphene based optical devices in the visible spectrum.
Here, we report a unique approach that avoids these limitations and
implements graphene into optoelectronic devices working in the visible
spectrum. The approach relies on controlling nonradiative energy transfer
between colloidal quantum-dots and graphene through gate-voltage induced
tuning of the charge density of graphene. We demonstrate a new class
of large area optoelectronic devices including fluorescent display
and voltage-controlled color-variable devices working in the visible
spectrum. We anticipate that the presented technique could provide
new practical routes for active control of light–matter interaction
at the nanometer scale, which could find new implications ranging
from display technologies to quantum optics
In-111-pentetreotide uptake in accessory spleen: A potential pitfall in somatostatin receptor scintigraphy
WOS: 000373691900020PubMed: 2709587
Low dark current N structure superlattice MWIR photodetectors
Commercially available read out integrated circuits (ROICs) require the FPA to have high dynamic resistance area product at zero bias (R(0)A) which is directly related to dark current of the detector. Dark current arises from bulk and surface contributions. Recent band structure engineering studies significantly suppressed the bulk contribution of the type-II superlattice infrared photodetectors (N structure, M structure, W structure). In this letter, we will present improved dark current results for unipolar barrier complex supercell superlattice system which is called as "N structure". The unique electronic band structure of the N structure increases electron-hole overlap under bias, significantly. N structure aims to improve absorption by manipulating electron and hole wavefunctions that are spatially separated in T2SLs, increasing the absorption while decreasing the dark current. In order to engineer the wavefunctions, we introduce a thin AlSb layer between InAs and GaSb layers in the growth direction which also acts as a unipolar electron barrier. Despite the difficulty of perfect lattice matching of InAs and AlSb, such a design is expected to reduce dark current. Experiments were carried out on Single pixel with mesa sizes of 100 x 100 - 700 x 700 mu m photodiodes. Temperature dependent dark current with corresponding R(0)A resistance values are reported