https://iopscience.iop.org/article/10.1088/0022-3727/49/41/413002/pdf

Intrinsic and extrinsic doping of ZnO and ZnO alloys

The development of three-dimensional (3-D), characterisation techniques with high spatial and mass resolution is crucial for understanding and developing advanced materials for many engineering applications as well as for understanding natural materials. In recent decades, atom probe tomography (APT), which combines a point projection microscope and time-of-flight mass spectrometer, has evolved to be an excellent characterisation technique capable of providing 3-D nanoscale characterisation of materials with sub-nanometer scale spatial resolution, with equal sensitivity for all elements. This review discusses the current state, as of APT instrumentation, new developments in sample preparation methods, experimental procedures for different material classes, reconstruction of APT results, the current status of correlative microscopy, and application of APT for microstructural characterisation in established scientific areas like structural materials as well as new applications in semiconducting nano...

/pdf/three-dimensional-nanoscale-characterisation-of-materials-by-30gmt17ll9.pdf

Three-dimensional nanoscale characterisation of materials by atom probe tomography

We present a highly sensitive detection of skin cancer using a novel water-based terahertz (THz) metamaterial (MM) and a semiconductor film. We apply the application of terahertz pulsed imaging in reflection geometry for the study of skin tissue and related cancers. As a refractive index (RI) sensing application of the proposed device, with placing different sensing materials in the biosensor design, the effective RI will also change that in turn leads to measuring the sensitivity of the biosensor to detect the normal skin and basal cell carcinoma. The RI figure of merit (FOM) value of the proposed device is much higher than that of the sensor using a semiconductor film to detect biomarkers in the literature. Significantly, the sensitivity increases by about 117 $\mu {\mathrm{ m}}$ /RIU and the RI FOM increases by more than 20.53. This results from a combination of size-related factors, leading to field enhancement accompanying strong field localization. We observed the resonance-frequency shift of the THz MM following the RI changing of the detected skin. The dip reflectance resonance has a blue shift for normal skin. Finally, we suggest that this water-based MM can be used to the control of the gene expression. The advantage of our design depends on two factors. First, we used the MM structure that has micro-scale, and the smaller the size of the structure, the more sensitive to the changes in the RI. Second, we used water in our structure, which is very well-suited to the human body, highly bio-absorbable and inexpensive, and abundantly found in nature.

Water-Based Terahertz Metamaterial for Skin Cancer Detection Application

http://smeng.ucsd.edu/wp-content/uploads/Effects-of-laser-energy-and-wavelength-on-the-analysis-of-LiFePO4-using-laser-assisted-atom-probe-tomography.pdf

Effects of laser energy and wavelength on the analysis of LiFePO4 using laser assisted atom probe tomography

Atom probe tomography has without any doubt become a routine technique to analyze the detailed three-dimensional chemistry of materials at the nanoscale. This article provides a general overview of what APT can reliably do today and what it might do tomorrow in terms of material characterization. The recent achievements in the analysis of new materials and new materials structures are first presented allowing some speculation on future possible developments. The ability to provide unique quantitative chemical information to link processing to device performance is then reviewed in the context of the recent nanowire and gate structures analyses. Finally examples of the systematic use of atom probe tomography to explore material behaviors and kinetic processes controlling microstructure evolution are presented.

On the current role of atom probe tomography in materials characterization and materials science

Wide-bandgap zinc oxide (ZnO) semiconductors and nanowires have become important materials for electronic and photonic device applications. In this work, we report the growth of well-aligned single-crystal ZnO nanowire arrays on sapphire substrates by chemical vapor deposition and the development of atom probe tomography, an emerging nanoscale characterization method capable of providing deeper insight into the three-dimensional distribution of atoms and impurities within its structure. Using a metal-catalyst-free approach, the influence of the growth parameters on the orientation and density of the nanowires were studied. The resulting ZnO nanowires were determined to be single crystalline, with diameter on the order of 50 nm to 150 nm and length that could be controlled between 0.5 μm to 20 μm. Their density was on the order of high 108 cm−2 to low 109 cm−2. In addition to routine characterizations using scanning and transmission electron microscopy, x-ray diffraction, photoluminescence, and Raman spectroscopy, we developed the atom probe tomography technique for ZnO nanowires, comparing the voltage pulse and laser pulse modes. In-depth analysis of the data was carried out to determine the accurate chemical composition of the nanowires and reveal the incorporation of nitrogen impurities. The current–voltage characteristics of individual nanowires were measured to determine their electrical properties.

Atom Probe Tomography of Zinc Oxide Nanowires

In this work, we report the growth and nanoscale characterization of single crystal zinc oxide nanowires synthesized by thermal chemical vapor deposition. Scanning electron microscopy, high-resolution transmission electron microscopy, x-ray diffraction, photoluminescence and Raman spectroscopy confirmed the high quality nature of the materials. To analyze their electrical properties, terahertz time domain spectroscopy was used. Atom probe tomography experiments and analysis were successfully developed and carried out, for the first time, on individual ZnO nanowires. This analysis revealed the incorporation of small concentration levels of atomic nitrogen homogeneously in nanowires grown when nitrogen gas was present during synthesis. Atom probe tomography can yield valuable information on the distribution of dopants and other impurities in wide bandgap semiconductor nanostructures and thus help understand better the material characteristics at the nanoscale.

Nanoscale characteristics of single crystal zinc oxide nanowires

With the increasing worldwide need for energy, fossil fuels will not be able to keep up with demand in the coming decades Solar energy is one of the best solutions to this problem with the advantages of being clean and sustainable Among the various designs of solar cells, dye-sensitized solar cells provide relatively high efficiency with large scale for a low cost [1] Conventional dye-sensitized solar cells operate with light harvesting organic dye molecules adsorbed at the interface between TiO 2 nanoparticles and a hole-conducting liquid electrolyte [2] However, new combinations of materials potentially present an opportunity to further improve the performance and lower the cost of solar cells One such promising approach is to use quantum dots (QDs) instead of the organic materials as the main photosensitive constituent Several types of semiconductor QDs, including CdSe [3], CdS [4] and InP [5], have been investigated to realize quantum dot sensitized solar cells by taking advantage of the tunable absorption spectrum of the QDs through changes in their size Complementarily to this approach, it is desirable to use a semiconductor material with a high structural uniformity and surface area as the framework on which to attach these QDs and achieve efficient electron transport, such as well-aligned ZnO nanowires [6]

InP/ZnS core-shell quantum dots sensitized ZnO nanowires for photovoltaic devices

Quantum dot (QD) functionalized nanowire arrays are attractive structures for low cost high efficiency solar cells. QDs
have the potential for higher quantum efficiency, increased stability and lifetime compared to traditional dyes, as well as
the potential for multiple electron generation per photon. Nanowire array scaffolds constitute efficient, low resistance
electron transport pathways which minimize the hopping mechanism in the charge transport process of quantum dot
solar cells. However, the use of liquid electrolytes as a hole transport medium within such scaffold device structures
have led to significant degradation of the QDs. In this work, we first present the synthesis uniform single crystalline ZnO
nanowire arrays and their functionalization with InP/ZnS core-shell quantum dots. The structures are characterized using
electron microscopy, optical absorption, photoluminescence and Raman spectroscopy. Complementing
photoluminescence, transmission electron microanalysis is used to reveal the successful QD attachment process and the
atomistic interface between the ZnO and the QD. Energy dispersive spectroscopy reveals the co-localized presence of
indium, phosphorus, and sulphur, suggestive of the core-shell nature of the QDs. The functionalized nanowire arrays are
subsequently embedded in a poly-3(hexylthiophene) hole transport matrix with a high degree of polymer infiltration to
complete the device structure prior to measurement.

Photovoltaic devices based on quantum dot functionalized nanowire arrays embedded in an organic matrix

We report the realization of hybrid nanostructures that combine inorganic InP/ZnS core-shell quantum dots and wide bandgap ZnO nanowires with an organic polymer matrix compound, which can potentially enable optoelectronic devices novel functionalities, including photovoltaics. The ZnO nanowires were synthesized by thermal chemical vapor deposition prior to functionalization with the quantum dots and embedding into a poly-3(hexylthiophene) hole transport matrix. The nanostructures were precisely characterized using photoluminescence, Raman spectroscopy, x-ray diffraction, scanning and high resolution transmission electron microscopy. Unique atomic scale resolution analysis of the nanostructures was performed using energy dispersive x-ray spectroscopy mapping and atom probe tomography for the first time.

Nicholas Harris

Papers

Atom Probe Tomography of Zinc Oxide Nanowires

Nanoscale characteristics of single crystal zinc oxide nanowires

InP/ZnS core-shell quantum dots sensitized ZnO nanowires for photovoltaic devices

Photovoltaic devices based on quantum dot functionalized nanowire arrays embedded in an organic matrix

Hybrid nanostructures based on quantum dots and nanowires