Sergio M.M. Coelho

Electrical characterization of defects introduced during electron beam deposition of Pd schottky contacts on n-type Ge

We have investigated by deep level transient spectroscopy the hole and electron trap defects introduced in n-type Ge during electron beam deposition (EBD) of Pd Schottky contacts. We have also compared the properties of these defects with those introduced in the same material during high-energy electron irradiation. Our results show that EBD introduces several electron and hole traps at and near the surface of Ge. The main defect introduced during EBD has electronic properties similar to those of the V–Sb complex, or E center, introduced during high-energy particle irradiation of Ge. This defect has two levels E0.38 and H0.30 that correspond to its (−−,−) and (−,0) charge states.

A compact streak camera for 150 fs time resolved measurement of bright pulses in ultrafast electron diffraction

We have developed a compact streak camera suitable for measuring the duration of highly charged subrelativistic femtosecond electron bunches with an energy bandwidth in the order of 0.1%, as frequently used in ultrafast electron diffraction (UED) experiments for the investigation of ultrafast structural dynamics. The device operates in accumulation mode with 50 fs shot-to-shot timing jitter, and at a 30 keV electron energy, the full width at half maximum temporal resolution is 150 fs. Measured durations of pulses from our UED gun agree well with the predictions from the detailed charged particle trajectory simulations.

Effects of hydrogen, oxygen, and argon annealing on the electrical properties of ZnO and ZnO devices studied by current-voltage, deep level transient spectroscopy, and Laplace DLTS

Effects of annealing ZnO in hydrogen, oxygen, and argon have been investigated using deep level transient spectroscopy (DLTS) and Laplace-DLTS (LDLTS) measurements. Current-voltage (IV) measurements indicate a decrease in zero–bias barrier height for all the annealed samples. Conventional DLTS measurements reveal the presence of three prominent peaks in the un-annealed and annealed samples. A new peak with an activation enthalpy of 0.60 eV has been observed in the H2 annealed samples, while an estimated energy level of 0.67 eV has been observed in Ar annealed samples. O2 annealing does not introduce new peaks but causes a decrease in the concentration of the E3 peak and an increase in concentration of the E1 peak. The concentrations of all the intrinsic defects have decreased after H2 and Ar annealing; with Ar annealing giving peaks with the lowest concentrations. The E2 peak anneals out after annealing ZnO in Ar and H2 at 300 °C. From the annealing behaviour of E3, we have attributed to transition metal ...

Electrical characterization of defects introduced in n-Ge during electron beam deposition or exposure

Schottky barrier diodes prepared by electron beam deposition (EBD) on Sb-doped n-type Ge were characterized using deep level transient spectroscopy (DLTS). Pt EBD diodes manufactured with forming gas in the chamber had two defects, E0.28 and E0.31, which were not previously observed after EBD. By shielding the samples mechanically during EBD, superior diodes were produced with no measureable deep levels, establishing that energetic ions created in the electron beam path were responsible for the majority of defects observed in the unshielded sample. Ge samples that were first exposed to the conditions of EBD, without metal deposition (called electron beam exposure herein), introduced a number of new defects not seen after EBD with only the E-center being common to both processes. Substantial differences were noted when these DLTS spectra were compared to those obtained using diodes irradiated by MeV electrons or alpha particles indicating that very different defect creation mechanisms are at play when too ...

A comparative study of the electrical properties of Pd/ZnO Schottky contacts fabricated using electron beam deposition and resistive/thermal evaporation techniques

very low reverse currents of the order of 10 � 10 A at a reverse voltage of 1.0 V whereas the e-beam deposited contacts have reverse currents of the order of 10 � 6 A at 1.0 V. Average ideality factors have been determined as (1.43 60.01) and (1.66 60.02) for the resistively evaporated contacts and e-beam deposited contacts, respectively. The IV barrier heights have been calculated as (0.721 60.002) eV and (0.624 60.005) eV for the resistively evaporated and e-beam deposited contacts, respectively. Conventional DLTS measurements reveal the presence of three prominent defects in both the resistive and e-beam contacts. Two extra peaks with energy levels of 0.60 and 0.81 eV below the conduction band minimum have been observed in the e-beam deposited contacts. These have been explained as contributing to the generation recombination current that dominates at low voltages and high leakage currents. Based on the reverse current at 1.0 V, the degree of rectification, the dominant current transport mechanism and the observed defects, we conclude that the resistive evaporation technique yields better quality Schottky contacts for use in solar cells and ultraviolet detectors compared to the e-beam deposition technique. The 0.60 eV has been identified as possibly related to the unoccupied level for the doubly charged oxygen vacancy, Vo 2þ . V C 2011 American Institute of Physics. [doi:10.1063/1.3658027]

The origin of defects induced in ultra-pure germanium by Electron Beam Deposition

The creation of point defects in the crystal lattices of various semiconductors by subthreshold events has been reported on by a number of groups. These observations have been made in great detail using sensitive electrical techniques but there is still much that needs to be clarified. Experiments using Ge and Si were performed that demonstrate that energetic particles, the products of collisions in the electron beam, were responsible for the majority of electron-beam deposition (EBD) induced defects in a two-step energy transfer process. Lowering the number of collisions of these energetic particles with the semiconductor during metal deposition was accomplished using a combination of static shields and superior vacuum resulting in devices with defect concentrations lower than

Experimental Observation of Intrinsic Localized Modes in Germanium

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Characterization of the E(0.31) defect introduced in bulk n-Ge by H or He plasma exposure

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Ar plasma induced deep levels in epitaxial n-GaAs

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Electrical Characterization of Defects Introduced in n-Type N-Doped 4H-SiC during Electron Beam Exposure

, the measurement limit of our deep level transient spectroscopy (DLTS) system. High energy electrons and photons that samples are typically exposed to were not influenced by the shields as most of these particles originate at the metal target thus eliminating these particles as possible damage causing agents. It remains unclear how packets of energy that can sometimes be as small of 2eV travel up to a