Since the automation of the electron backscatter diffraction (EBSD) technique, EBSD systems have become commonplace in microscopy facilities within materials science and geology research laboratories around the world. The acceptance of the technique is primarily due to the capability of EBSD to aid the research scientist in understanding the crystallographic aspects of microstructure. There has been considerable interest in using EBSD to quantify strain at the submicron scale. To apply EBSD to the characterization of strain, it is important to understand what is practically possible and the underlying assumptions and limitations. This work reviews the current state of technology in terms of strain analysis using EBSD. First, the effects of both elastic and plastic strain on individual EBSD patterns will be considered. Second, the use of EBSD maps for characterizing plastic strain will be explored. Both the potential of the technique and its limitations will be discussed along with the sensitivity of various calculation and mapping parameters.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S1431927611000055

A review of strain analysis using electron backscatter diffraction.

Ordered magnetic nanostructures: fabrication and properties

High-resolution elastic strain measurement from electron backscatter diffraction patterns: New levels of sensitivity

One dimensional nanostructured materials

In recent years, GaN nanorods are emerging as a very promising novel route toward devices for nano-optoelectronics and nano-photonics. In particular, core-shell light emitting devices are thought to be a breakthrough development in solid state lighting, nanorod based LEDs have many potential advantages as compared to their 2 D thin film counterparts. In this paper, we review the recent developments of GaN nanorod growth, characterization, and related device applications based on GaN nanorods. The initial work on GaN nanorod growth focused on catalyst-assisted and catalyst-free statistical growth. The growth condition and growth mechanisms were extensively investigated and discussed. Doping of GaN nanorods, especially p-doping, was found to significantly influence the morphology of GaN nanorods. The large surface of 3 D GaN nanorods induces new optical and electrical properties, which normally can be neglected in layered structures. Recently, more controlled selective area growth of GaN nanorods was realized using patterned substrates both by metalorganic chemical vapor deposition (MOCVD) and by molecular beam epitaxy (MBE). Advanced structures, for example, photonic crystals and DBRs are meanwhile integrated in GaN nanorod structures. Based on the work of growth and characterization of GaN nanorods, GaN nanoLEDs were reported by several groups with different growth and processing methods. Core/shell nanoLED structures were also demonstrated, which could be potentially useful for future high efficient LED structures. In this paper, we will discuss recent developments in GaN nanorod technology, focusing on the potential advantages, but also discussing problems and open questions, which may impose obstacles during the future development of a GaN nanorod based LED technology.

GaN based nanorods for solid state lighting

https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=32797

Mechanism for spontaneous growth of GaN nanowires with molecular beam epitaxy

https://www.ctcms.nist.gov/%7Edavydov/06Bert_GaN%20%20and%20AlGaN%20NWs%20JCG_287_522.pdf

Spontaneously grown GaN and AlGaN nanowires

We report steady-state and time-resolved photoluminescence (TRPL) measurements on individual GaN nanowires (6–20 μm in length, 30–940 nm in diameter) grown by a nitrogen-plasma-assisted, catalyst-free molecular-beam epitaxy on Si(111) and dispersed onto fused quartz substrates. Induced tensile strain for nanowires bonded to fused silica and compressive strain for nanowires coated with atomic-layer-deposition alumina led to redshifts and blueshifts of the dominant steady-state PL emission peak, respectively. Unperturbed nanowires exhibited spectra associated with high-quality, strain-free material. The TRPL lifetimes, which were similar for both relaxed and strained nanowires of similar size, ranged from 200 ps to over 2 ns, compared well with those of low-defect bulk GaN, and depended linearly on nanowire diameter. The diameter-dependent lifetimes yielded a room-temperature surface recombination velocity S of 9×103 cm/s for our silicon-doped GaN nanowires.

https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=32785

Steady-state and time-resolved photoluminescence from relaxed and strained GaN nanowires grown by catalyst-free molecular-beam epitaxy

We have grown GaN and AlGaN nanowires on Si (111) substrates with gassource molecular beam epitaxy (MBE). No metal catalysts were used. The nanowires displayed a number of interesting materials properties, including room-temperature luminescence intensity greater than that of free-standing HVPE-grown GaN, relaxed lattice parameters, and the tendency of nanowires dispersed in solvents to align in response to electric fields. The wires were well separated, 50–250 nm in diameter, and grew to lengths ranging from 2 µm to 7 µm. Transmission electron microscopy indicated that the wires were free of defects, unlike the surrounding matrix layer.

/pdf/catalyst-free-growth-of-gan-nanowires-6qncwgtl55.pdf

Catalyst-free growth of GaN nanowires

The location ofGaN nanowires is controlled with essentially perfect selectivity using patterned SiN x prior to molecular beam epitaxy growth. Nanowire growth is uniform within mask openings and absent on the mask surface for over 95% of the usable area of 76 mm diameter substrate. The diameters of the resulting nanowires are controlled by the size of the mask openings. Openings of approximately 500 nm or less produce single nanowires with symmetrically faceted tips.

Alexana Roshko

Papers

Mechanism for spontaneous growth of GaN nanowires with molecular beam epitaxy

Spontaneously grown GaN and AlGaN nanowires

Steady-state and time-resolved photoluminescence from relaxed and strained GaN nanowires grown by catalyst-free molecular-beam epitaxy

Catalyst-free growth of GaN nanowires

Controlled Nucleation of GaN Nanowires Grown with Molecular Beam Epitaxy