Suwit Kiravittaya

Bio: Suwit Kiravittaya is an academic researcher from Naresuan University. The author has contributed to research in topics: Quantum dot & Molecular beam epitaxy. The author has an hindex of 39, co-authored 144 publications receiving 3942 citations. Previous affiliations of Suwit Kiravittaya include Chulalongkorn University & Leibniz Institute for Solid State and Materials Research.

Advanced quantum dot configurations

Abstract: We present an overview on approaches currently employed to fabricate advanced quantum dot configurations by epitaxial growth. Widely investigated self-assembled quantum dots, i.e. In(Ga)As/GaAs and (Si)Ge/Si, are first introduced. Different quantum dot structures can be derived from In(Ga)As quantum dots by combining them with in situ etching, by layer stacking or by using them as stressors. Other fabrication methods include droplet epitaxy and multilayer deposition on hole patterned substrates.The combination of bottom–up and top–down methods results in absolute position control of self-assembled quantum dots. We review these 'seeded quantum dot crystals' in detail. Finally, we discuss a promising approach to realize quantum dot crystals with controlled spatial and optical properties.

Formation of lateral quantum dot molecules around self-assembled nanoholes

Abstract: We fabricate groups of closely spaced self-assembled InAs quantum dots (QDs)—termed lateral QD molecules—on GaAs (001) by a combination of molecular-beam epitaxy and AsBr3 in situ etching. An initial array of homogeneously sized nanoholes is created by locally strain-enhanced etching of a GaAs cap layer above InAs QDs. Deposition of InAs onto the nanoholes causes a preferential formation of the InAs QD molecules around the holes. The number of QDs per QD molecule ranges from 2 to 6, depending on the InAs growth conditions. By decreasing the substrate temperature, the number of QDs per QD molecule increases, but the statistical distribution is wider due to a reduced In atom diffusion length. Our photoluminescence investigation documents the nanohole and QD molecule formation step by step and confirms the high crystal quality of these structures. An analysis of the nanohole geometry as a function of annealing time and InAs filling allows us to propose a model for the QD molecule formation process.

Principles and applications of micro and nanoscale wrinkles

Abstract: In this review, we summarize recent and interesting applications of micro and nanoscale wrinkles. Fluidic studies are comprehensively highlighted for various wrinkled nanochannels. Wrinkling as a mechanical characterization tool is also explained. As a new feature, wrinkles are employed to modify structures or physical properties of nanomaterials. It is promising to apply wrinkling for strain-engineering of graphene. We believe that wrinkling offers entirely new research perspectives in micro and nanotechnologies as well as in material sciences and engineering.

Lab-in-a-tube: detection of individual mouse cells for analysis in flexible split-wall microtube resonator sensors.

Abstract: We report a method for the precise capturing of embryonic fibroblast mouse cells into rolled-up microtube resonators. The microtubes contain a nanometer-sized gap in their wall which defines a new type of optofluidic sensor, i.e., a flexible split-wall microtube resonator sensor, employed as a label-free fully integrative detection tool for individual cells. The sensor action works through peak sharpening and spectral shifts of whispering gallery modes within the microresonators under light illumination.

Engineering atomic and molecular nanostructures at surfaces

Abstract: The fabrication methods of the microelectronics industry have been refined to produce ever smaller devices, but will soon reach their fundamental limits. A promising alternative route to even smaller functional systems with nanometre dimensions is the autonomous ordering and assembly of atoms and molecules on atomically well-defined surfaces. This approach combines ease of fabrication with exquisite control over the shape, composition and mesoscale organization of the surface structures formed. Once the mechanisms controlling the self-ordering phenomena are fully understood, the self-assembly and growth processes can be steered to create a wide range of surface nanostructures from metallic, semiconducting and molecular materials.

Intrinsic ripples in graphene

Abstract: The stability of two-dimensional (2D) layers and membranes is subject of a long standing theoretical debate. According to the so called Mermin-Wagner theorem, long wavelength fluctuations destroy the long-range order for 2D crystals. Similarly, 2D membranes embedded in a 3D space have a tendency to be crumpled. These dangerous fluctuations can, however, be suppressed by anharmonic coupling between bending and stretching modes making that a two-dimensional membrane can exist but should present strong height fluctuations. The discovery of graphene, the first truly 2D crystal and the recent experimental observation of ripples in freely hanging graphene makes these issues especially important. Beside the academic interest, understanding the mechanisms of stability of graphene is crucial for understanding electronic transport in this material that is attracting so much interest for its unusual Dirac spectrum and electronic properties. Here we address the nature of these height fluctuations by means of straightforward atomistic Monte Carlo simulations based on a very accurate many-body interatomic potential for carbon. We find that ripples spontaneously appear due to thermal fluctuations with a size distribution peaked around 70 \AA which is compatible with experimental findings (50-100 \AA) but not with the current understanding of stability of flexible membranes. This unexpected result seems to be due to the multiplicity of chemical bonding in carbon.

Interfacing single photons and single quantum dots with photonic nanostructures

Abstract: Quantum dots embedded in photonics nanostructures provide unprecedented control over the interaction between light and matter. This review gives an overview of the theoretical principles involved, as well as applications ranging from high-precision quantum electrodynamics experiments to quantum-information processing.

X-ray diffraction of III-nitrides

Abstract: The III-nitrides include the semiconductors AlN, GaN and InN, which have band gaps spanning the entire UV and visible ranges. Thin films of III-nitrides are used to make UV, violet, blue and green light-emitting diodes and lasers, as well as solar cells, high-electron mobility transistors (HEMTs) and other devices. However, the film growth process gives rise to unusually high strain and high defect densities, which can affect the device performance. X-ray diffraction is a popular, non-destructive technique used to characterize films and device structures, allowing improvements in device efficiencies to be made. It provides information on crystalline lattice parameters (from which strain and composition are determined), misorientation (from which defect types and densities may be deduced), crystallite size and microstrain, wafer bowing, residual stress, alloy ordering, phase separation (if present) along with film thicknesses and superlattice (quantum well) thicknesses, compositions and non-uniformities. These topics are reviewed, along with the basic principles of x-ray diffraction of thin films and areas of special current interest, such as analysis of non-polar, semipolar and cubic III-nitrides. A summary of useful values needed in calculations, including elastic constants and lattice parameters, is also given. Such topics are also likely to be relevant to other highly lattice-mismatched wurtzite-structure materials such as heteroepitaxial ZnO and ZnSe.

Optofluidic microsystems for chemical and biological analysis

Abstract: Optofluidics - the synergistic integration of photonics and microfluidics - has recently emerged as a new analytical field that provides a number of unique characteristics for enhanced sensing performance and simplification of microsystems. In this review, we describe various optofluidic architectures developed in the past five years, emphasize the mechanisms by which optofluidics enhances bio/chemical analysis capabilities, including sensing and the precise control of biological micro/nanoparticles, and envision new research directions to which optofluidics leads.