Hexagonal boron nitride is distinguished among solid-state materials with luminescent properties as a material to create single-photon sources efficiently emitting at room temperature. In this work, it is demonstrated that helium ion irradiation with fluences of (1–5) × 1014 ion/cm2 increases the ultraviolet radiation intensity with a maximum at a wavelength of 320 nm due to the formation of new luminescent centers. The subsequent electron irradiation further increases the intensity of 320 nm luminescence apparently due to the formation of carbon-containing defects in the volume of hBN through recombination-enhanced migration. On the contrary, the intense helium ion irradiation stimulates the formation of nonradiative recombination centers, which reduce the lifetime of nonequilibrium charge carriers.

Wide bandgap orthorhombic polymorph of gallium oxide (kappa-Ga2O3) possessing a high spontaneous polarization grown on wurtzite-type semiconducting substrates is considered to create a high mobility electron channel suitable for applications. Such kappa-Ga2O3 layers are composed of hexagon microprisms whose properties affect the lateral electric conductance. In this work, the structure and recombination properties of extended defects in individual "suspended" thin microprisms are investigated with transmission and scanning electron microscopy techniques (STEM, HR-TEM) including cathodoluminescence (CL-SEM). It is established that the microprism is composed of six equisized orthorhombic domains bounded by twin domain boundaries (TDBs) along the directions <110>. Twin domain contains a parallel array of antiphase boundaries (APB) of a high density stretched in the [010] direction. APBs possess steps or interruption and can form double oppositely shifted spatially separated layers (APB dipoles). TDBs on majority of their length are incoherent and serve as the border for the APB terminations. Panchromatic CL maps reveal either enhanced or reduced intensity of APB without noticeable spectral changes. CL intensity enhancement is proposed to be due to enhanced electron-hole generation caused by excess scattering of primary electron beam by APBs in thin films while, in fact, APB exhibits enhanced nonradiative recombination activity.

Numerous diverse grown-in point defects in hexagonal boron nitride exhibit properties of single photon emitters stimulating the development of controllable methods for their local formation. In this work the defects created in hexagonal boron nitride by helium ion irradiation were investigated by means of cathodoluminescence and Raman spectroscopy. The irradiation with ion fluence above 10(15) cm(-2) resulted in a new Raman spectral band at about 1295 cm(-1), which can be attributed to the formation of vacancies or divacancies. The intensity of the defect-related luminescence was found to vary non-monotonically with ion fluence and possessed a maximum at about 10(14) cm(-2). On the basis of this result a new procedure to fabricate light emitting discs by means of the focused helium ion beam was suggested and demonstrated.

Представлены результаты экспериментального исследования реальной структуры тонких пленок κ-фазы оксида галлия. Методами дифракции обратно отраженных электронов в сканирующем электронном микроскопе и просвечивающей электронной микроскопии установлено, что микро-монокристаллы κ-оксида галлия состоят из совокупности трех типов поворотных доменов орторомбической симметрии, повернутых друг относительно друга на угол 120° вокруг оси роста. Монокристаллические домены характеризуются большой плотностью прямолинейных антифазных границ, формирующих при своем пересечении структуру значительной доли доменных границ.

The change in the intensity of cathodoluminescence of hexagonal boron nitride in the short-wavelength spectral region upon electron beam excitation is investigated. It is shown that the intensity of the peak at a wavelength of 215 nm, associated with the band-to-band transitions, decreases during electron excitation and tends to a stationary value, whereas the intensity of the peak at 320 nm increases under electron irradiation. This band is likely caused by the formation of luminescence centers under electron irradiation.

o_gogina@mail.ru Abstract. Hexagonal boron nitride (hBN) is characterized by two main point defect -related luminescence bands with the peaks in visible, at 650 nm (1.9 eV), and UV, 320 nm (4 eV) spectral regions, which possess the properties of single photon emitters (SPE). We demonstrate that sufficiently long irradiation of thin hBN flakes in a scanning electron microscope with electron beam with energies from 5 keV to 20 keV and the flux equal or more than 10 15 cm -2 s -1 resulted in a drastic increase in the integral intensity of the 4 eV band previously associated with carbon -related defects. The effect of the irradiation induced luminescence enhancement increases with the decrease of the electron beam energy that corresponds well with the calculated energy losses in thin samples. An increase in the concentration of carbon -related defects introduced into the sample from surface carbon contaminated layer via recombination -enhanced migration or changes of the charge state of existing defects could be supposed to be mechanisms of the observed effect. The obtained results demonstrate the possibility of local control of UV SPE concentration in hBN.

Systems with a focused ion beam, using gas field ion sources, are described. The principles of operation and ways of formation of these sources, in which the effective ionization region is determined by sizes of a single atom, are considered in the historical context. The described systems have a wide range of applications, both in the field of scanning ion microscopy in combination with various analytical methods and in the field of high-resolution modification of electrical, optical, magnetic, and other properties of materials. This modification, based on ion-induced changes in the structure of material, is most pronounced in crystalline semiconductors, superconductors, and magnets.

Исследовано изменение интенсивности катодолюминесценции гексагонального нитрида бора в коротковолновой части спектра в процессе возбуждения электронным пучком. Показано, что интенсивность пика на длине волны 215 нм, связываемого с переходами зона–зона, убывает в процессе возбуждения электронами и стремится к стационарному значению, в то время как интенсивность пика на длине волны 320 нм возрастает под действием электронного облучения. Эта полоса, вероятно, обусловлена образованием центров люминесценции под действием электронного облучения.

Aluminum nitride films have been synthesized by reactive magnetron sputtering on n-Si(100) substrates. AlN layers with thicknesses from 2 to 150 nm were obtained to establish a correlation between the structure of the films and their electrical conductivity. Electron microscopy revealed that the amorphous structure of the films passes to nanocrystalline one while moving away from the substrate surface. Films with thicknesses below 20 nm had a high conductivity: up to 10 (Ω cm)–1; with an increase in thickness the conductivity dropped to 10–7 (Ω cm)–1. The high conductivity of thin AlN layers is believed to be due to the high density of the boundaries of grains built-in into amorphous matrix.

The results of an experimental study of the real structure of thin films of κ-phase gallium oxide are reported. It has been established by electron backscattering diffraction in a scanning electron microscope and by transmission electron microscopy that gallium oxide single microcrystals consist of three types of rotating domains of the orthorhombic symmetry, which are rotated relative to each other around the growth axis by an angle of 120°. Single-crystal domains are characterized by a high density of straight antiphase boundaries, which, when intersecting, form a significant fraction of the domain wall structure.

Описаны системы со сфокусированным ионным пучком, использующие газовые автоионные источники. В историческом контексте рассмотрены принципы работы таких источников и способы их формирования, эффективная область ионизации в которых определяется размерами одного атома. Описываемые системы имеют широкий спектр приложений как в области сканирующей ионной микроскопии в сочетании с различными аналитическими методами, так и в области модификации с высоким разрешением электрических, оптических, магнитных и других свойств материалов. Такая модификация основана на ионно-индуцированном изменении структуры материала и наиболее ярко выражена в кристаллических полупроводниках, сверхпроводниках и магнетиках.

Пленки нитрида алюминия синтезированы с помощью метода реактивного магнетронного напыления на кремниевых подложках n-Si (100). Слои AlN толщиной от 2 до 150 нм получены с целью установления корреляции между строением пленок и их электропроводностью. С помощью электронной микроскопии установлено, что по мере удаления от поверхности подложки аморфное строение пленки переходило к нанокристаллическому. Пленки с толщинами до 20 нм имели высокую проводимость до 10 (Ом·см)–1, при увеличении толщины проводимость резко падала до 10–7 (Ом·см)–1. Предполагается, что высокая проводимость тонких слоев AlN обусловлена высокой плотностью границ зерен, встроенных в аморфную матрицу.

The structural properties of twin domain boundaries (TDB) and antiphase boundaries (APB) in individual thin, hexagonal prismatic microcrystals of kappa-Ga2O3 grown on GaN/sapphire template with HVPE were investigated with electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). The microcrystals were composed from the domains with three in-plane 120 degrees rotational orientations. It was found that every individual twin domain contains a parallel array of APBs of a high density stretched in the [010] direction. APBs possess steps or interruption and can form double oppositely shifted spatially separated layers (APB dipoles). TDBs on majority of their length are incoherent being not strictly flat and serve as the border for the APBs interruptions. Panchromatic cathodoluminescence mapping of the microcrystals revealed that not all TDBs and APBs reduced its intensity. The interruptions and steps of APBs were proposed to be the main origin of the excess charged carrier recombination. A model of the atomic structure in the vicinity of the defects is proposed and the assumption about the formation of local high strain regions and dangling bonds was made.

The impact of irradiation with a focused helium ion beam and an electron beam on the cathodoluminescence (CL) of hexagonal boron nitride was investigated. It was shown that the irradiation with helium ions resulted in a decrease in the intensity of CL in the region of 200–700 nm. Subsequent irradiation with electrons results in an increase in the intensity of the 2 eV CL band compared with its intensity in pristine material.

Point defects in wide-bandgap semiconductors, in particular in hexagonal boron nitride, are promising candidates for single-photon emitters, used in quantum informatics. We investigated cathodoluminescence of ion beam induced defects in hexagonal boron nitride, as well as the effect of prolonged electron irradiation on the intensity of the luminescence. It has been shown that the intensity of both band-to-band emission and defect related emission decreased after ion irradiation, and during subsequent electron irradiation the intensity of 2 eV luminescence band increased, whereas the intensity of other bands remained unchanged.

Defect structure and electric properties of n‐type silicon samples subjected to multienergy oxygen implantation and subsequent multistage thermal treatments at different high temperatures and durations are investigated with the help of transmission electron microscopy (TEM), capacitance–voltage ( C ( V )), and deep level transient spectroscopy (DLTS) techniques. Well spatially separated layers in the depth consisting of three predominant types of defects—threading dislocations (TDs), oxygen precipitates (OPs) together with diverse extended structural defects and OPs only—are observed with TEM. While the properties of DLTS spectra from the layer with TDs coincide well with dislocation‐related ones reported in numerous previously published articles, the spectra from the OP layer are found to show unusual distinct property: the low‐temperature tail of DLTS peak does not or very weakly depend on the rate window. A simplified semiquantitative model is proposed based on a big positive charge of OP layer revealed from C ( V ) measurements. The model explains the unusual property to be due to an increase of the Coulomb‐like attractive potential upon electron emission from the electronic states of the OPs giving rise to logarithmic emission kinetics.

Hexagonal boron nitride is a promising material of modern optoelectronics. Point defects in this material can serve as single-photon sources. In this paper we investigate the modification of the luminescent properties of hexagonal boron nitride by means of local irradiation with focused gallium and helium ion beams. It is demonstrated that the intensity of band-to-band cathodoluminescence monotonically decreases with increasing ion fluence for both gallium and helium. The luminescence band of about 2 eV may become more intense after exposure to He ions with certain ion fluence. The effect of complete quenching of luminescence after gallium irradiation is used to estimate the diffusion length of excess charge carriers. Keywords: point defects, cathodoluminescence, scanning helium ion microscope, excess charge carriers.

Herein, the influence of the oxygen flow on the formation of metastable polymorphs of gallium oxide (Ga 2 O 3 ) grown by halide vapor phase epitaxy (HVPE) on c‐plane patterned sapphire substrates (PSS), on gallium nitride (GaN) templates, and on m‐plane smooth sapphire substrates is reported. X‐ray diffraction, scanning electron microscopy, and cathodoluminescence are used to identify different polymorphic phases. The samples deposited on bare PSS exhibit faceted growth of the α‐Ga 2 O 3 on the cones of the sapphire substrate and the formation of the κ‐Ga 2 O 3 between the cones. In contrast, growth on GaN templates results in hexagonal columns of κ‐Ga 2 O 3 which produce a continuous smooth layer upon coalescence. The growth of Ga 2 O 3 on m‐plane sapphire substrates results in overgrown pyramids of the α‐phase. For all types of substrates, the variation of the oxygen flow affects only the thickness and coalescence of Ga 2 O 3 layers. Thus, the growth of Ga 2 O 3 metastable polymorphs is mainly influenced by the form, orientation, and symmetry of the substrate and shows a weak dependence on stoichiometry.

Hexagonal boron nitride is a promising material of modern optoelectronics. Point defects in this material can serve as single-photon sources. In this paper we investigate the modification of the luminescent properties of hexagonal boron nitride by means of local irradiation with focused gallium and helium ion beams. It is demonstrated that the intensity of band-to-band cathodoluminescence monotonically decreases with increasing ion fluence for both gallium and helium. The luminescence band of about 2 eV may become more intense after exposure to He ions with certain ion fluence. The effect of complete quenching of luminescence after gallium irradiation is used to estimate the diffusion length of excess charge carriers.

Dislocations introduced by Vickers tip microindentation of an a-plane free-standing semi-insulating Fe-doped GaN halide vapor phase epitaxy (HVPE) crystal were investigated by means of cathodoluminescence and scanning transmission electron microscopy techniques. Detailed combined analyses of both spectral properties and the core structure of the introduced a-screw dislocations revealed that Fe-doped GaN exhibit not only dislocation-bound emission at ∼3.35 eV of perfect a-screw dislocations previously found in such kind of samples but also luminescent bands at 3.1–3.2 and 3.3 eV due to dissociated a-screw dislocations and extended dislocation nodes previously observed only in low-resistance n-GaN. For the first time, all these luminescent bands were observed together in the same sample. Structural studies revealed the coexistence of the dislocations with the dissociated and the perfect core as well as with extended dislocation nodes, thus establishing a correlation between previously observed luminescence bands and a fine dislocation core structure.