Emission Secondary Electron Microscopy Research Articles

Direct Measurement of the Electrical Abruptness of a Nanowire p-n Junction.

Electrostatic potential maps of GaAs nanowire, p-n junctions have been measured via off-axis electron holography and compared to results from in situ electrical probing, and secondary electron emission microscopy using scanning electron microscopy. The built-in potential and depletion length of an axial junction was found to be 1.5 ± 0.1 V and 74 ± 9 nm, respectively, to be compared with 1.53 V and 64 nm of an abrupt junction of the same end point carrier concentrations. Associated with the switch from Te to Zn dopant precursor was a reduction in GaAs nanowire diameter 3 ± 1 nm that occurred prior to the junction center (n = p) and was followed by a rapid increase in Zn doping. The delay in Zn incorporation is attributed to the time required for Zn to equilibrate within the Au catalyst.

Structural and compositional mapping of a phase-separated Langmuir–Blodgett monolayer by X-ray photoelectron emission microscopy

The structure and composition of phase-separated Langmuir–Blodgett monolayer films comprised of mixtures of arachidic acid (C 19H 39COOH) and perfluorotetradecanoic acid (C 13F 27COOH) were characterized using a combination of X-ray photoelectron emission microscopy (X-PEEM), secondary electron emission microscopy (SEEM) and atomic force microscopy (AFM). X-PEEM provides high lateral spatial resolution and is directly sensitive to the elemental and chemical (functional group) composition of these ultrathin films through the chemical sensitivity of NEXAFS spectroscopy; AFM provides high-resolution imaging, both in terms of lateral and vertical (height) film topography. SEEM provides additional structural and electronic information through work function and electron scattering effects. The combination is used for chemical mapping of the phase-separated domains in the monolayer film. Our results directly confirm previous AFM measurements that suggested that the discontinuous domains are enriched in arachidic acid, whereas the surrounding continuous domain is a mixture of both arachidic acid and perfluorotetradecanoic acid.

Development of an X-ray photoemission electron microscopy system with multi-probes, and its application to surface imaging at static and dynamic states.

We have developed a new X-ray photoemission electron microscopy system combined with low energy electron microscopy, photoemission electron microscopy, mirror electron microscopy (MEM), secondary electron emission microscopy (SEEM) and Auger electron emission microscopy, which provides multi-angle information on the distribution and change of element, chemical state, structure, etc. at solid surfaces under the working conditions such as high temperature and gas atmosphere. The performance of each microscopical method was examined and typical images are presented. The dynamic behaviour of fabricated surfaces has been imaged in real time by SEEM and MEM.

Hydrogen termination and electron emission from CVD diamond surfaces: a combined secondary electron emission, photoelectron emission microscopy, photoelectron yield, and field emission study

Abstract The effect of hydrogen termination on the electron emission properties of CVD diamond surfaces is investigated. Three kinds of electron emission process, namely secondary electron emission (SEM), photoelectron emission, and field emission are compared on hydrogen free and hydrogen terminated surfaces. Electron beam stimulated desorption was employed to desorb hydrogen from the diamond surface and to pattern H-free areas on otherwise H-covered surfaces. The hydrogen terminated areas give strong electron emission in contrast to the hydrogen free surfaces for all emission processes studied. In particular, the hydrogen free patterns are imaged with comparable contrast by SEM and photoelectron emission microscopy (PEEM). This indicates that the hydrogen termination on diamond surfaces reduces the energy barrier for electron emission by lowering the electron affinity of diamond surface. This is confirmed by a drastic difference in the onset for field emission between the hydrogenated and hydrogen free parts of the same CVD diamond film. It is further demonstrated by yield spectroscopy that the threshold for electron emission below the gap of diamond is lowered by the hydrogenation process.

Electron Beam Induced Damage of NaNO3 Single Crystals: An Energy, Temperature, and Quantum State Resolved Study

Electron beam induced damage of NaNO{sub 3} single crystals is examined using laser resonance enhanced multiphoton ionization detection of the neutral desorption products, post-irradiation temperature-programmed desorption (TPD), secondary electron emission microscopy (SEEM), and Auger electron spectroscopy (AES). The damage initially involves destruction of the nitrate group and production of O ({sup 3}P{sub J}) and NO ({sup 2}II) fragments with nonthermal energy distributions. Specifically, the O ({sup 3}P{sub J}) J state distribution measured at 100 eV incident electron energy is 5:1.5:0.25 for J = 2:1:0, the NO ({sup 2}II) vibrational state distribution is 1:0.56:0.35:0.40:0.23 for {nu} = 0:1:2:3:4, and the NO ({sup 2}II{sub 1/2,3/2}) rotational distribution has a high population of the upper ({sup 2}II{sub 3/2}) spin-orbit component. Production and desorption of these nonthermal fragments are dominated by the decay of {l{underscore}brace}NO{sub 3}{sup {minus}}{r{underscore}brace}*. At higher electron fluences, thermalized NO, O{sub 2}, and NO{sub 2} are also produced and released, through the NO{sub 2} is a minor product. The authors suggest that the formation and desorption of thermalized NO and O{sub 2} both involve NO{sub 2}{sup {minus}} defect states and unimolecular dissociation of NO{sub 3}{asterisk}. This is supported by the observation that the NO and O{sub 2} yields have the samemore » temperature dependence which is well described by the sum of two Maxwell-Boltzmann type equations with activation energies of 0.16 {+-} 0.03 and 0.010 {+-} 0.004 eV. O{sub 2} gas is also released in post-irradiation thermal cycling from 110 to 440 K with peaks at {approximately}260 and {approximately}340 K. The authors associate the post-irradiation TPD of O{sub 2} with reactions involving O atoms released during thermal decomposition of {l{underscore}brace}NO{sub 2}{sup {minus}}{hor{underscore}ellipsis}O{r{underscore}brace} and ONOO{sup {minus}}. The SEEM image shows damage features, and the AES spectra indicate that the irradiated region is depleted in both nitrogen and oxygen relative to Na. The elemental composition shows Na{sub 2}O as a final product of the NaNO{sub 3} radiation decomposition. The 100 eV electron beam damage cross section is at least {approximately}10{sup {minus}16} cm{sup 2}.« less

A new approach to nuclear microscopy: the ion–electron emission microscope

A new multidimensional high lateral resolution ion beam analysis technique, ion–electron emission microscopy (IEEM) is described. Using MeV energy ions, IEEM is shown to be capable of ion beam induced charge collection (IBICC) measurements in semiconductors. IEEM should also be capable of microscopically and multidimensionally mapping the surface and bulk composition of solids. As such, IEEM has nearly identical capabilities as traditional nuclear microprobe analysis, with the advantage that the ion beam does not have to be focused. The technique is based on determining the position where an individual ion enters the surface of the sample by projection secondary electron emission microscopy. The x–y origination point of a secondary electron, and hence the impact coordinates of the corresponding incident ion, is recorded with a position sensitive detector connected to a standard photoemission electron microscope (PEEM). These signals are then used to establish coincidence with IBICC, atomic, or nuclear reaction induced ion beam analysis signals simultaneously caused by the incident ion.

Asymmetric secondary electron emission flux in ferroelectric KTiOPO4 crystal

It is shown that secondary electron emission current from ferroelectric domains with opposite directions of spontaneous polarization in ferroelectric KTiOPO4 crystals (KTP) is substantially asymmetric. The effect originates from asymmetry of elementary electron processes in noncentrosymmetric crystals. A nondestructive method of ferroelectric domain observation by secondary electron emission microscopy in KTP crystals is developed, which enables observation of a domain grating in periodically poled KTP frequency doubler.

A simple method for surface and ultrathin film characterization

The method depends on monitoring variations of secondary electron emission as a function of changes in surface structure and composition. By measuring the crystal current i cc and its variation with incident beam energy, E, surface changes can be measured rapidly and precisely. The principle of the method is already used qualitatively in secondary electron emission microscopy. If E is adjusted to give zero crystal current ( E zcc), and changes are followed from either variations in i cc or E zcc, then the measurements obtained during adorption are comparable to (but can be more precise than) those obtained from Auger spectroscopy. Results are presented for copper surfaces during cleaning cycles and during the adsorption of lead overlayers. Various applications can be envisaged, especially for rapid changes during segregation, diffusion or desorption.

Cathodoluminescence and electrical anisotropy from α and β dislocations in plastically deformed gallium arsenide

Infrared cathodoluminescence (IR-CL) micrographs were taken of surfaces perpendicular (II2) and parallel (021) to the bend axis [II2] of n-type GaAs single crystals bend at 700°C in four-point bending to introduce α (Ga) and β (As) dislocations. At the bend center, light and dark checkered patterns associated with dislocations could be observed only in the IR-CL micrographs but not by optical, standard infrared, or secondary electron emission microscopy. No significant changes related to the type of dislocation (α or β) or dislocation density were observed either in the IR-CL peak half-width or peak position at E=1.411 eV. However, decreases of 40−70% in the relative IR-CL intensity were observed in the bend samples containing predominantly α or β dislocations. To study electrical anisotropy in the deformed samples, Hall measurements as a function of temperature were made of sections cut parallel and perpendicular to the [II2] bend axis to eliminate effects due to point defects and impurities. The results indicate that relative to the unbent control sample, the conductivity and mobility of sampples with dislocations oriented parallel to the current direction were slightly enhanced, while decreases of 50−60% were noted when the dislocations were aligned perpendicular to the current direction. When oriented in the parallel mode, an increase in conductivity and mobility was noted from both types of dislocations, with the samples containing β dislocations showing a larger increase than those with α dislocations. In contrast, when the dislocations were oriented in the mobility than thoise with β dislocations. The observed electrical anisotropy is discussed in the light of current models describing specular (or difuse) electron scattering dislocations.

Cathodoluminescence study of plastically deformed GaAs

Infrared cathodoluminescence (IR–CL) micrographs were taken of surfaces perpendicular (11¯2) and parallel (021) to the bend axis [11¯2] of GaAs single crystals bent at 700 °C in four-point bending to introduce α-Ga and β-As dislocations. At the bend center, light and dark checkered patterns associated with dislocations could be observed only in the IR–CL micrographs but not by optical, infrared, or secondary electron emission microscopy. Dislocation densities to ρ ≈ 5 × 106 cm−2 could be determined nondestructively to within 20% of the theoretical values. No significant changes related to the type of dislocation or dislocation density were observed either in the peak half-width or peak position at E = 1.411 eV. However, decreases of 40–70% in the relative IR–CL intensity were observed in the bent samples with predominantly α or β dislocations.