D2 Peak Research Articles

Photoluminescence analysis of high-resistivity CdZnTe:In single crystals obtained by annealing

High-resistivity In-doped CdZnTe (CZT:In) single crystals were obtained by annealing under Te atmosphere. Photoluminescence spectrum was used to investigate annealed CZT:In single crystals. The results indicated that (D0, X) peak which is related to the crystal quality appeared after annealing. The donor–acceptor pair peak DAP mainly originated from the complex consisted of the donor In+Cd and the acceptor [In+CdV2−Cd]−. The intensity of DAP peak decreased, which might suggest that the impurities were removed. Moreover, Dcomplex peak containing two peaks for as-grown CZT:In consisted of Cd vacancy-related (D1) and dislocation-related (D2) defects. However, the intensity of D2 peak was very low because of the elimination of Cd inclusions after annealing. And the intensity of D1 peak increased because of the increase of Cd vacancies by evaporating for a long time.

Molecular dynamics study of the vibrational pattern of ring structures in the Raman spectra of vitreous silica

AbstractRaman scattering spectra of silica glass models were studied by means of molecular dynamics computer simulation. The study principally aimed at the inspection of the assignment of the defect bands of the Raman spectra of a‐SiO2 proposed by Galeener and co‐workers (Galeener FL, Barrio RA, Martinez E, Elliott RJ. Phys. Rev. Lett. 1984; 53: 2429). The results of the study have shown that the D2 peak at 606 cm−1 can probably be related to the presence of three‐membered rings in a‐SiO2, whereas the D1 feature at 495 cm−1 correlates with the presence of both three‐ and four‐membered rings, and can therefore, be used for structural characterisation of silica glasses only with care. Copyright © 2008 John Wiley & Sons, Ltd.

Engineering of Dislocation-Loops for Light Emission from Silicon Diodes

Luminescence properties of silicon light emitting diodes with engineered dislocation loops were investigated. Dislocation loops were formed by Si+-ion implantation above and below metallurgical p+-n junction followed by an annealing step. The diodes showed characteristic dislocation (D-band) and band-to-band luminescence. Measurements of carrier-injection level dependence of the D-band signal intensity were performed. The results are in agreement with the model for dislocation luminescence, which suggests rediative transition between two, dislocation-related shallow levels. A gradual blue-shift of the D-band peak positions was observed with an increase in the carrier injection level in electroluminescence and photoluminescence. A supposition about existence of strong Stark effect for the excitonic dislocation states allows explaining the observations. Namely, in the build-in electric field of the p-n junction the exciton energies are red-shifted. The injected charge carriers lower the field and thus cause the blue-shift of the peak positions. A fitting of the data using the quadratic Stark effect equation suggests 795 meV for the spectral position of D1 peak at 300 K and 0.0186 meV/(kV/cm)2 for the characteristic constant.

Changes in illusory ankle movements induced by tendon vibrations during the delayed recovery phase of stretch-shortening cycle fatigue: An indirect study of muscle spindle sensitivity modifications

This study examined the perceived movement velocity induced by tendon vibrations during the delayed recovery phase of a stretch-shortening cycle (SSC)-type exercise characterized by 2 to 4 days of neuromuscular and proprioceptive impairments. Seven subjects performed until exhaustion series of unilateral rebounds involving mostly the triceps surae muscle group. Fatigue effects were quantified for the exercised and non-exercised legs through muscle soreness and maximal voluntary plantarflexion test (MVC) performed immediately before (PRE) and after the SSC exercise, and repeated 2 days later (D2). At PRE and D2, mechanical vibrations at 40, 60, 80, 100, and 120 Hz were applied to distal tendons of the exercised ankle. For each vibration, the subjects had to reproduce the perceived movement velocity with the non-exercised ankle. According to previous studies, the sole exercised leg was characterized by a D2 peak of muscle soreness associated, in the MVC test, with significant decreases in maximal force and mean soleus muscle activity. As compared to the PRE test and in all subjects, the vibrations applied at D2 to the tendon of the fatigued ankle extensor muscles led to significant decreases in the perceived movement velocity at 80 and 100 Hz, but to an increased one at 40 Hz. In contrast, vibrations applied to the tendon of the non-fatigued ankle flexor muscle did not result in any significant change. These results suggest that the delayed recovery phase of SSC fatigue is characterized by changes in muscle proprioception, which may partly result from a decreased sensitivity of the primary endings.

Quantitative detection of tiny amounts of helium isotopes in a hydrogen isotope atmosphere using a standard-resolution quadrupole mass spectrometer

This article describes a new method to quantitatively detect extremely small amounts of helium (and eventually other inert gases) in complex gaseous mixtures, even in the presence of very high concentrations of hydrogen isotopes, despite using a conventional (i.e., standard-resolution) quadrupole mass spectrometer. This is accomplished by means of two nonevaporable getter (NEG) pumps, which effectively remove all active components in the original gas mixture with particular regard to hydrogen isotopes. Obviously, noble gases are preserved. The gas sample to be analyzed is initially admitted in a first chamber equipped with a NEG pump operating at high temperature (≈450°C), in order to remove most of the active gases quickly. The residual gas mixture is then allowed to expand through a gate valve into the analysis chamber, where a second NEG pump, operating at room temperature, completes the selective pumping action and removes to high degree hydrogen isotopes and other chemically active gases. The turbomolecular pump, which is used to evacuate the chamber, is excluded during the analysis. The results of extensive tests carried out with a fully automated facility built at ENEA Frascati are reported, demonstrating the effectiveness of this method which allows detection of He4∕D2 peak ratios as small as ≈2.5×10−7. During these tests, a quadrupole mass spectrometer which can operate in both standard- and high-resolution modes has been used. This latter operating mode has been selected, when necessary, in order to provide evidence for the absence of deuterium contributions to mass 4.

Microstructural and defect population change in electron beam irradiated Ge:SiO 2 MCVD glasses in the conditions of refractive index change writing

Electron spin resonance (ESR) and ultra violet (UV) optical absorption spectra are measured in Ge:SiO 2 glasses elaborated by modified chemical vapor deposition (MCVD) and irradiated by an electron beam of medium energy (10–50 keV). The doses (a few C/cm 2) like the electron energy used, correspond to conditions for writing refractive index change for optical applications. These data yielded information on defect population changes. Raman spectroscopy was used for correlating these changes to microstructural changes. We point out a 5.1 eV absorption bleaching like surprisingly the one occurring under 5 eV laser irradiation correlated to an absorption increases around (4.4 and 5.8 eV). E′ centres are also produced. More specifically, we found in a previous work two domains of irradiation parameters for samples with large Ge content for which specific volume increases or decreases. We thus precise in this paper that (1) when compaction occurs, detectable by surface topography depression and D2 peak intensity increase, Si E′ centres are produced and a diamagnetic component absorbing strongly at 6.1 eV that may arise from sixfold coordinated Ge, (2) when expansion dominates, D2 peak does not decrease at all but long range order changes, detectable by modification of transverse optical (TO) and longitudinal optical (LO) mode intensity. In this case, Ge E′ and Ge(1) dominate and the previous absorption at 6.1 eV disappears. In addition, an absorption peak appears at 3.1 eV from an unknown defect.

Slow post-orogenic cooling in a deeply eroded orogen: Reindeer Zone, Trans-Hudson Orogen, Saskatchewan

We present 40Ar/39Ar hornblende and muscovite data from a 200 km transect across the northern flank of the Paleoproterozoic Trans-Hudson Orogen (THO) exposed along Reindeer Lake in Saskatchewan, Canada. The transect crosses a series of distinct lithotectonic domains that experienced pressure–temperature (P–T) conditions of 600–730 °C at 4.5–6.0 kbar (1 kbar = 100 MPa) during D2 peak metamorphism at 1820–1790 Ma. The distribution of 40Ar/39Ar hornblende ages shows that most of the transect cooled through approximately 500 °C by ca. 1765 Ma, with two significant exceptions. At the north end of the transect, older ages in the Peter Lake Domain (up to 2200 Ma) suggest that this region did not experience high-grade metamorphism that affected the rest of the transect and may indicate a structural break between these Archean rocks and the Cree Lake Zone to the north. In the south-central part of the transect, U–Pb (monazite, titanite) and 40Ar/39Ar (hornblende, muscovite) ages indicate that rocks in the vicinity of the Duck Lake Shear Zone, a ductile thrust zone separating the Kisseynew and La Ronge domains, cooled at a rate of 6 °C/Ma and that cooling was delayed by ca. 20–25 million years relative to that of adjacent regions. Based on generic thermal–tectonic models for large hot orogens, we suggest that delayed cooling in the vicinity of the shear zone reflects post-orogenic thermal relaxation of lower crustal isotherms that were perturbed by the effects of convergence.

Structures prepared by implantation of silicon with nitrogen and annealing under high hydrostatic pressure

The effect of treatment up to 1130 °C under hydrostatic argon pressure up to 1.1 GPa on the structure of silicon implanted with nitrogen, Si:N (nitrogen dose, D=2×10 16 cm −2, ion energy, E=150 keV) was investigated by TEM, photoluminescence (PL) and other methods. The high-temperature pressure treatment produces typically strongly disturbed buried nitrogen-containing layers. The Fz-Si:N samples treated at 450 °C—HP indicate the PL peaks at about 0.81 eV (the dislocation-related D1 peak) with the intensity increasing with HP (no PL at 0.81 eV was detected for the sample treated under 0.01 GPa), and at about 0.93 eV (the dislocation-related D3 peak). The Fz-Si:N sample treated at higher temperature (650 °C) and under the highest pressure (1.1 GPa) indicates the presence of PL only at about 0.87 eV (the D2 dislocation-related line). Our investigations help in understanding the mechanisms of creation of buried insulating layers in nitrogen-implanted silicon.

Relaxation peaks associated with the oxygen-ion diffusion in La2−xBixMo2O9 oxide-ion conductors

The effects of bismuth doping on the oxygen-ion diffusion in oxide-ion conductors La 2-x Bi x Mo 2 O 9 (x = 0.05, 0.1, and 0.15) have been studied by both internal friction and dielectric relaxation techniques. Two internal friction peaks of relaxation type (P 1 and P 2 peak) were observed at a measurement frequency of 4 Hz around 380 and 430 K, respectively. As for the dielectric measurement, a prominent dielectric relaxation peak (P d ) was found in all the Bi-doped samples around 700 K at a measurement frequency of 50 kHz, which actually consists of two sub-peaks (denoted as P d1 and P d2 peak). With increasing Bi-doping content, two peaks shift to higher temperature and decrease in height, while the activation energy of both peaks increases. The main reason was interpreted as the introduction of the lone-pair electrons of bismuth, which tends to block the diffusion of oxygen ion.

Temperature behaviour of extended defects in solar grade silicon investigated by photoluminescence and EBIC

Spatially resolved photoluminescence and EBIC were used to characterise a sample of multicrystalline silicon in the temperature range 80–300 K. The dislocation related lines in the spectrum-D1, D2, D3 and D4 correlate with the total recombination activity measured by EBIC. The temperature dependent EBIC behaviour was utilised to access the contamination level at the dislocations in low quality regions of the sample. The temperature dependence of D1 line shows a maximum at about 150 K. The decrement of D1 peak area upon temperature decreasing below 150 K could be related to the appearance of D3 and D4 lines in the photoluminescence spectra. The peak widths of D1 and D2 show opposite temperature dependence. D1 width decreases and D2 becomes broader upon decreasing temperature. Two additional lines with energies below the energy of band-to-band luminescence were observed together with the D bands at 80 K. They could be related to phonon replication of the band edge luminescence peak and can be seen on FZ-Si too.

Dielectric relaxation studies on the submicron crystalline La 2Mo 2O 9 oxide-ion conductors

Submicron crystalline La 2Mo 2O 9 bulk samples with grain size of about 0.3 μm were successfully synthesized by sol–gel method and sintering process assisted by phase transformation. In the dielectric measurement, two prominent relaxation peaks with almost the same height (P d1 at lower-temperature and P d2 at higher-temperature) are observed in temperature spectrum as well as in frequency spectrum, which are associated with the short-distance diffusion of oxygen vacancies. The activation energies and relaxation times at infinite temperature of these two peaks are deduced as (1.22 eV, 3.3×10 −16 s) and (1.35 eV, 5.9×10 −16 s), respectively. The DC conductivity of the submicron crystalline samples, which is about 0.02 S/cm when extrapolated to 800 °C, is much smaller than that of the macrocrystalline samples. The reciprocal of the peak height for P d1 peak is linearly proportional to temperature, while that for P d2 peak is temperature independent. The reason for the co-appearance and the possible relaxation dynamics of the two peaks are discussed.

Assessment of left atrial appendage wall velocities by transesophageal tissue Doppler echocardiography: A clinical study in patients with sinus rhythm

To assess left atrial appendage (LAA) wall velocities, 42 patients in sinus rhythm underwent tissue Doppler interrogation during a clinically indicated transesophageal echocardiography. Color Doppler (B-mode and M-mode) and pulsed Doppler of LAA walls were obtained and analyzed in all patients. Color-coded tissue Doppler rendered a qualitative assessment of LAA wall, depicting both the timing and the sequence of LAA contraction. With pulsed Doppler interrogation, a triphasic signal was recorded in all patients, consisting of a positive wave (D1), followed by a biphasic wave (positive D2 and negative D3). Peak velocities of D1, D2, and D3 were 6.1 ± 2, 20.1 ± 7, and 16.1 ± 5 cm/s, respectively. Mean coefficient of variation of LAA wall velocities was 6%, significantly lower than that of LAA percentage area change (29%). Compared with patients with abnormal relaxation, patients with normal mitral inflow had higher D1 peak velocities (7.3 ± 1.2 vs 4.3 ± 1 cm/s, respectively; P <.0001). Time sequence of ECG, LAA flow, and mitral inflow indicates that D1 component of LAA wall occurs in early diastole and is likely due to the upward movement of the mitral ring toward the base of the LAA wall. In conclusion, evaluation of LAA wall using tissue Doppler is feasible and reproducible. Although color tissue Doppler analysis allows a qualitative assessment, pulsed Doppler gives new quantitative insights for the comprehensive assessment of LAA wall dynamics, which complements the information obtained with flow interrogation. (J Am Soc Echocardiogr 2002;15:425-32.)

The physiology of sexual arousal in the human female: a recreational and procreational synthesis.

Changes induced by human sexual arousal serve reproductive and recreational functions. The current sexual phase model (desire, excitation, orgasm, and resolution) conveys little about this duarchy. Lack of spontaneous sexual desire in a third of nonclinic females indicates that the D phase needs splitting into D1 (the spontaneous [endogenous] activation of desire) and D2 (desire activated by sexual excitation at and during the E phase). Attempts to link D1 with reproduction by studies monitoring it over the menstrual cycle revealed a D1 peak just before or at ovulation, but its reliability is criticized because of the poor identification of the time of ovulation. Sexual arousal initiates enhanced genital blood flow, leading to the formation of a neurogenic transudate, lubricating the vagina, partly buffering its acidity, and increasing its oxygen tension all features that enhance spermatozoal function and survival. Orgasm occurs with vaginal and uterine contractions. The latter have been misinterpreted as powering rapid sperm transport to facilitate fertilization, but such fast transport would lead to the tubal deposition of noncapacitated, incompetent spermatozoa. Vagino-cervico elevation, however, delays rapid sperm transport and allows the initiation of decoagulation and sperm capacitation before the elevation resolves. The fastest transport of spermatozoa from cervix to the fallopian tubes occurs in the nonaroused female by uterine/subendometrial smooth muscle peristalsis. There is some evidence that even this may be reduced for a time after coitus, adding to the transport delay. If a number of the changes induced by sexual arousal are inadequately expressed, sexual as well as reproductive dysfunctions could arise.

Studies of the ultrasonic properties of triglycine sulfate (tgs) single crystal

The longitudinal ultrasonic attenuation and velocity were measured in triglcyine sulfate (TGS) single crystal over the temperature range of 30–100°C. It was found that the peak of the relative ultrasonic attenuation near the second-order phase transition is lower in the heating process than that in the cooling process, and its height decreases with the increasing frequency. Hence, the peak should be associated with the process of changing temperature and the measuring frequency. Another ultrasonic attenuation peak, which corresponds to the P D2 peak discovered by other scientists, was also found in the experiment at 5.56 MHz. However, in experiments at 13.3 MHz and 30.8 MHz, such a peak was not observed. Considering these phenomena, it is suggested that this peak does not occur above the Curie point and is closely related to the interaction between domains.

Oxidation-induced traps near SiO2/SiGe interface

Using an Al/SiO2(wet)/Si0.9Ge0.1/n–Si/Al capacitor structure, effects of oxidation on bulk trap and interface states near the SiO2/SiGe interface are investigated. Two peaks at the energy levels of 0.23 eV (D1) and 0.40 eV (D2) below the conduction band edge are observed with the capacitance deep level transient spectroscopy (DLTS) method. The DLTS measurement results show a characteristic feature of interface states for the D1 peak. The interface state distribution obtained by the capacitance–voltage method also has a high density (6.9×1012/cm2 eV) peak at an energy level of 0.23 eV below the conduction band edge. The Si–O– dangling bonds are thought to be the source of the D1 peak. The annealing behaviors of the D2 peak show that D2 is a divacancy related bulk trap. The capture cross section and the trap density for the bulk trap D2 are 2.06×10−15/cm2 and 1.8×1014/cm3, respectively. The density of D2 is significantly reduced after low temperature postmetallization annealing.

The Use of Derivative Spectrophotometry for the Determination of Acyclovir and Diloxanide Furoate in Presence of Impurity or Degradation Product

Second (D2) and third (D3) derivatives spectrophotometry have been developed for the determination of acyclovir in the presence of guanine (its main impurity) and diloxanide furoate in the presence of diloxanide (its degradation product). The methods depend upon measuring D2 and D3 peak amplitudes at 269 and 262 nm for acyclovir and at 260 and 270 nm for diloxanide furoate in 0.1 N hydrochloric acid. Accuracy of analysis with the proposed derivative spectrophotometric procedure is significantly greater than the classical methods.

Influence of misfit dislocation interactions on photoluminescence spectra of SiGe on patterned Si

The Si substrates were patterned and etched to create arrays of squares separated by 10 μm trenches. Some edges of these squares were ion implanted with a large dose of Ge to create damaged regions that act as misfit dislocation nucleation centers during molecular beam epitaxy of a 700 nm Si0.90Ge0.10 lattice mismatched layer. Low temperature photoluminescence spectra of the material were obtained with an illuminated area selected so that only one type of edge implant was studied at a time. Sub-band gap luminescence peaks associated with dislocations, D lines, were found only in the squares with implants, consistent with electron microscopy results that showed that the control squares had few misfit dislocations. A large D1 luminescence peak was observed in samples that consisted of intersecting arrays of misfit dislocations, while only a small peak was present in specimens implanted such that dislocations lay in only one in-plane direction. These results are interpreted to mean that the D1 peak is intrinsic to the dislocations themselves and not to impurity gettering. These observations further infer that D1 luminescence is related to dislocation kinks.

X-Ray Diffraction Studies of Sol-Gel Derived ORMOSILs Based on Combinations of Tetramethoxysilane and Trimethoxysilane

ORMOSILs have been prepared in the series TMOSx·MTMS(100 − x) (where TMOS is tetramethoxysilane; MTMS is methyltrimethoxysilane; x is mol% silane with respect to total silane for 0 ≤ x ≤ 100) by means of acid catalyzed, sol-gel processing. After drying at 60°C, small bulk samples were obtained of excellent optical clarity. Powder X-ray diffraction (XRD) patterns, in the range of 5 to 60°2Θ, were compared with that of fused silica. All the prepared samples were amorphous. Fused silica exhibits one broad peak, d2 centered at d-spacing 4.12 A. For the TMOS100 silica xerogel, the analogous broad peak had shifted slightly, to be centered at 3.88 A; and remained in about the same position as x was decreased for the series TMOSx·MTMS(100 − x). In addition, a second, broad peak, d1, was observed for the ORMOSIL series centered at the d-spacing 8.7 A for MTMS100 (i.e., x = 0) and increasing smoothly as x was increased, reaching 11.3 A for x = 70, and >11.3 A for x > 70. The intensity of d1 was found to have trebled, relative to the intensity of d2, on increasing the organic character of the matrix from TMOS70·MTMS30 to MTMS100. The d2 peak appearing at about 4 A for both fused silica and the ORMOSILs is assumed to be associated with the spacing between silicon atoms connected by means of an oxygen bridge. The Si–O–Si angle for silica xerogels is known to depend upon the nature of the sol-gel processing and is bigger than that of fused silica. The d1 peak may be associated with the spacing between silicons attached to methyl groups and indicative of channels of methyl groups in the structure. Alternatively, the d1 peak may have its origin in a preferred, discrete structural unit in the matrix for instance cubane based on a octameric silicon arrangement.

Raman spectra of coal-based graphite

Graphite formed in response to thermal contact metamorphism of coal bodies with magmatic intrusion is referred to as coal-based graphite. The first-order Raman spectrum of all the coal-based graphite taken from the Lutang area, Hunan Province exhibits a single Raman band near 1585cm-1, which comes directly from in-plane vibration of aromatic layer assigned to the E2g mode. Their Raman band of the structural defect in-plane can be divided into 2 types: one is the defect band (D peak) caused by the primary structural delect of the graphite in graphitization process, which is called D2-peak located at 1 360 cm-1; the other is the defect bank caused by the secondary structural defect in the graphite subject to tectonic shearing stress, which is called D1 peak located at 1370cm-1. The second Raman spectrum of the coal-based graphite shows three-dimensional lattice degree in the coal-based graphite. If the three-dimensional lattice of graphite is not well developed, it exhibits only a band of 2700cm-1; if the three-dimensional lattice of the coal-based graphite has been formed, the band of 2700cm-1 is split into two Raman bands, which are respectively located near 2681 cm-1 and near 2726cm-1, Raman band intensity ratio increases synchronously as the ordering degree of three-dimensional lattice increases regularly.

Molecular orbital calculations of vibrations in three-membered aluminosilicate rings

Ab initio, molecular orbital calculations at the 3–21G* level were carried out on H6Si3O9, [H6Si2AlO2]1−, [H6SiAl2O9]2−, and [H6A13O9]3− cyclic molecules in order to determine their structures and vibrational frequencies. These three-membered rings were found to have minima in their potential energy surfaces indicating stability of the species. The H6Si3O9 ring was found to be slightly non-planar, but the [H6SiAl2O9]2− and [H6Al33O9]3− configurations are more planar. Vibrational frequencies of the Raman-active, bridging oxygen “breathing” modes increase with Si4+ content. Galeener's (1982a, b) assignment of the D2 peak (606 cm−1) in the Raman spectrum of vitreous silica to an oxygen breathing mode in rings of three SiO4 tetrahedra is reconfirmed. Correlation of the ring breathing mode frequencies as a function of (AI/AI + Si) with Raman peaks in the SiO2-NaAlSiO4 system is high. Three-membered aluminosilicate rings are likely to exist and give rise to Raman peaks between 540 and 600 cm−1 in fully-polymerized aluminosilicate glasses.