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  • 1
    Electronic Resource
    Electronic Resource
    Spatial distribution of recombination centers in GaAs:Te: Effects of the doping level (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 987-992 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The distribution in liquid-encapsulated-Czochralski (LEC) GaAs:Te wafers of point and complex defects has been investigated together with their influence on the minority-carrier diffusion length L. Three wafers with different Te-doping concentration (2.2×1017, 4.5×1017, and 1.5×1018 cm−3) have been studied by means of the electron-beam-induced-current (EBIC) mode of scanning electron microscopy and of the surface photovoltage (SPV) method. The morphology and electrical activity of the defects observed across each wafer have been correlated to the formation and distribution of deep electronic levels, which are significantly affected by the tellurium concentration. The diffusion length has been found to be mainly controlled by deep levels associated with dislocations. EBIC localized measurements of L and of the net ionized free-carrier concentration provide evidence for the influence of Te concentration on impurity segregation at complex defects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357783
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  • 2
    Electronic Resource
    Electronic Resource
    The EL2 trap in highly doped GaAs:Te (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 6592-6595 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated highly doped GaAs:Te at different doping concentrations ((approximately-greater-than)1017 cm−3) to assess the presence of the EL2 trap. We have utilized both capacitance and current transient spectroscopy techniques. The crucial parameter for the detection of EL2 is the relative position of the electron quasi-Fermi level in the depletion region. The observed shift of the EL2 apparent activation energy with increasing doping concentration is also discussed. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360480
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  • 3
    Electronic Resource
    Electronic Resource
    Classification of chronic daily headache by International Headache Society criteria: limits and new proposals (1995)
    USA/Oxford, UK : Blackwell Science Ltd
    Cephalalgia 15 (1995), S. 0 
    Details
    ISSN: 1468-2982
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: We conducted a retrospective study of 150 patients with chronic daily headache (CDH) to determine how to categorize their headache according to the classification of the International Headache Society (IHS). All patients were first evaluated at Parma and Pavia Headache Centres (from January 1992 to March 1993) and had had headache for at least 15 days a month during the previous 6 months. Four patients were thereafter excluded due to poor reliability. The 146 patients who met our CDH criteria (92 with and 54 without clear-cut migraine attacks) could be classified into four groups: (i) chronic tension-type headache (CTTH)-27 patients; (ii) coexisting migraine plus CTTH-65 patients; (iii) unclassifiable daily headache-27 patients; and (iv) migraine and an unclassifiable interval headache-27 patients. Seventy-two percent of patients with CDH had migraine as the initial form of their headache. We therefore propose to revise the IHS classification for migraine, taking into account its evolution, and add two subcategories, migraine with interparoxysmal headache and chronic migraine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1468-2982.1995.1501037.x
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  • 4
    Electronic Resource
    Electronic Resource
    Bilateral asymmetry of cerebral blood velocity in cluster headache (1994)
    USA/Oxford, UK : Blackwell Science Ltd
    Cephalalgia 14 (1994), S. 0 
    Details
    ISSN: 1468-2982
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: In this study, 69 episodic cluster headache (CH) patients (40 in the active phase, 29 in remission period) underwent a complete TCD examination in order to verify the relationship between cerebral blood velocities (CBVs) and the clinical profile of the disease. Fifteen patients were examined during both phases, while 7 were monitored during a spontaneous attack. Sixty-three healthy sex and age-matched controls were also studied. We measured widespread, asymmetric CBV activation during the active phase, bilaterally in the anterior circulation and also in the posterior circulation. A relative reduction of CBV on the anterior cerebral artery pain side, also during remission, suggests a relationship between local vasodilation and the autonomic symptoms ipsilateral to pain during CH attacks.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1468-2982.1994.1405346.x
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  • 5
    Electronic Resource
    Electronic Resource
    Increased cerebral blood flow velocity induced by cold pressor test in migraine: a possible basis for pathogenesis? (1995)
    USA/Oxford, UK : Blackwell Science Ltd
    Cephalalgia 15 (1995), S. 0 
    Details
    ISSN: 1468-2982
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Noradrenergic nuclei of the locus coeruleus are believed to be involved in migraine pathogenesis. We recently demonstrated a typical intracerebral vasoconstriction after prolonged (5 min) exposure to cold pressor test (CPT), likely related to a central noradrenergic mechanism modulated at the locus coeruleus level and eliminated by pretreatment with clonidine. In the present study, we used transcranial Doppler ultrasonography to monitor blood flow velocity (BFV) changes to CPT in the middle cerebral artery (MCA) of migraine with (MA, n=12) and without (MO, n=15) aura subjects. CPT induced a significant increase in BFV and a concomitant decrease in the pulsatility index (PI), a pattern which is the opposite of the results obtained with controls. The results were comparable when controls were pretreated with clonidine. The MO patients produced an intermediate pattern between the MA and control subjects. A possible altered modulatory effect of opioids and/or serotonin on noradrenergic nuclei of the brainstem is the possible cause of the observed inverse response in migraine, suggesting intracerebral vasomotor instability in these patients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1468-2982.1995.1506494.x
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  • 6
    Electronic Resource
    Electronic Resource
    Double-junction effect in proton-irradiated silicon diodes (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 2013-2016 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This article concerns the existence of a double-junction effect in proton-irradiated silicon p+-ν-n+ (pin) diodes demonstrated by surface potential and optical-beam-induced current (OBIC) investigations. By increasing the diode biasing, the junctions existing at both ends in the irradiated devices move towards each other up to join, hence, causing a full depletion of the diodes. Due to the inhomogeneity of the electric field, however, the charge-carrier collection is strongly dependent on the position. The extent of the diode depletion layers at both ends and the shape of the electric field within the p+-ν-n+ diodes are determined as a function of the bias applied. Three-dimensional photocurrent maps obtained by OBIC profiles allow for imaging the double junction. The deep level analysis evidences the presence of irradiation-induced defects, which are responsible for the double-junction effect. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1495077
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  • 7
    Electronic Resource
    Electronic Resource
    Defects introduced in cadmium telluride by γ irradiation (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 4664-4666 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The properties peculiar to high resistivity CdTe:Cl are of great interest because of its application as a radiation detector. The compensation process responsible for the materials semi-insulating character implies the presence in the lattice of impurities and defects which have not yet been thoroughly characterized. The use of CdTe:Cl as a detector exposes the material to high fluxes of ionizing radiation which alter the crystal stoichiometry and affect the resulting electrical and optical properties, but few and scattered experimental data are available about radiation effects on this compound. In this work we have carried out an extensive investigation of the effects of γ irradiation on CdTe:Cl by photoinduced current transient spectroscopy analyses. We have identified the deep levels with activation energies up to midgap and we have followed their evolution with increasing irradiation doses up to 50 kGy, the dose which totally degrades the material detecting properties. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1351859
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  • 8
    Electronic Resource
    Electronic Resource
    Role of impurities on diffusion-induced defective states (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 5622-5627 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The defective states induced in floating zone Si by the heavy diffusion of dopants have been investigated by means of the electron beam-induced current method. By measuring the minority carrier diffusion length with the first order moment method, and by directly imaging the defects, their electrical activity has been analyzed. The diffused samples have subsequently been dry oxidized, so that the evolution of the electrical and morphological properties of the induced defects could be followed. Two sets of samples, one diffused with B and the other with B and Al, have been investigated in order to study the effects of the presence of Al. Significant improvements in the diffusion length have been observed in samples where Al had been codiffused, thus providing indication for the role played by Al on the electrical activity of bulk defective states.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351962
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  • 9
    Electronic Resource
    Electronic Resource
    Evaluation of diffusion length and surface recombination velocity in semiconductor devices by the method of moments (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 5964-5968 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The diffusion length and surface recombination velocity of the minority carriers are determined from electron beam induced current (EBIC) profiles on a semiconductor containing a barrier perpendicular to the scanned surface. The evaluation of both the parameters has been obtained by the procedure called "of the first moments,'' due to Donolato [C. Donolato, Appl. Phys. Lett. 43, 120 (1983)], which is based on the calculation of the first moment about the origin of two induced current profiles. This analysis, based on an exact integral property of the EBIC scans, allows evaluation of the diffusion length and the surface recombination without fitting the experimental profiles. In addition, it is easy to handle and can also be readily applied to real devices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350447
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  • 10
    Electronic Resource
    Electronic Resource
    Determination of minority-carrier diffusion length by integral properties of electron-beam-induced current profiles (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 2163-2168 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The diffusion length of minority carriers in n-type floating-zone Si samples is obtained with the electron-beam-induced current technique in planar configuration. The charge collection current data as a function of the beam-junction distance are analyzed on the basis of the "moment method'' developed by Donolato [C. Donolato, Solid-State Electron. 28, 1143 (1985)], which is based on the calculation of the variance of the derivative of the current profile. With respect to other methods reported in literature, this has the advantage that it requires no assumptions on the surface recombination velocity and thus provides a diffusion length value free from its influence. The data are also analyzed with the asymptotic method, which requires conventional assumptions on the surface recombination velocity. The comparison between the results has allowed us to test the capabilities of the above-mentioned method. Particular attention is paid to the injection level and its influence on bulk and surface properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349454
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