Influence of a Current on the Edge Structure Probed by Time-Resolved Transport Measurements

1994 ◽  
Vol 28 (2) ◽  
pp. 121-127 ◽  
Author(s):  
N. B Zhitenev ◽  
R. J Haug ◽  
K. v Klitzing ◽  
K Eberi
Keyword(s):  
Time Resolved ◽  
Edge Structure ◽  
Transport Measurements ◽  
A Current

Time-resolved Photoconductivity as a Probe of Carrier Transport in Microcrystalline Silicon

2006 ◽  
Vol 910 ◽  
Author(s):  
Steve Reynolds
Keyword(s):  
Density Of States ◽  
Carrier Mobility ◽  
Carrier Transport ◽  
Film Growth ◽  
Hole Mobility ◽  
Transport Parameters ◽  
Microcrystalline Silicon ◽  
Time Resolved ◽  
Transient Photoconductivity ◽  
Transport Measurements

AbstractThe use of transient photoconductivity techniques in the investigation of carrier transport in microcrystalline silicon is described. Results are presented which highlight variations in transport parameters such as carrier mobility and density of states with structure composition. Hole mobility is significantly enhanced by crystalline content in the film of 10% or less. The density of states inferred from transport measurements parallel to and at right angles to the direction of film growth differ somewhat, suggesting that transport may be anisotropic.

scholarly journals On the origin of negative target currents during laser ablation of polyethylene

2018 ◽  
Vol 167 ◽  
pp. 04006
Author(s):  
Domenico Delle Side ◽  
Anna Paola Caricato ◽  
Josef Krása ◽  
Vincenzo Nassisi
Keyword(s):  
Vacuum Chamber ◽  
Positive Charge ◽  
Active Phase ◽  
Time Resolved ◽  
Target Holder ◽  
Target Composition ◽  
Ultra High Molecular Weight ◽  
Different Thickness ◽  
Negative Target ◽  
A Current

The exposure of a target to a focused laser beam results in the occurrence of a time-varying current between the target itself and the grounded vacuum chamber. This current is composed by three distinct phases, namely the ignition phase, in which the laser pulse drives the electron emission, while electrons coming from the ground through the target holder balance the positive charge generated on the target. The active phase appears at post-pulse times and it is characterized by the presence of peaked structures in the time-resolved current, representing characteristics of the target composition. Lastly, the afterglow phase is determined by a current of electrons flowing from the target to the ground. During the active phase of the target current resulting from polymers ablation with an UV KrF laser, negative target current peaks are observed, whose origin is still unknown. We investigate the dependence of these current structures on the dimensions of the target, using ultra-high molecular weight polyethylene disks of different thickness.

scholarly journals Ballistic excited state dynamics revealed by polarized fs-XANES

2019 ◽  
Vol 205 ◽  
pp. 05014 ◽  
Author(s):  
Roseanne J. Sension ◽  
Nicholas A. Miller ◽  
Aniruddha Deb ◽  
Roberto Alonso-Mori ◽  
James M. Glownia ◽  
...  
Keyword(s):  
Excited State ◽  
Time Resolved ◽  
Edge Structure ◽  
X Ray ◽  
Excited State Dynamics ◽  
X Ray Absorption

Polarized time-resolved X-ray absorption near edge structure (XANES) is used to characterize the sequential ballistic excited state dynamics of two B12 vitamers: cyanocobalamin and adenosylcobalamin. Excitation at 550 nm and 365 nm is used to resolve axial and equatorial contributions to the excited state dynamics.

A microsecond time resolved x-ray absorption near edge structure synchrotron study of phase transitions in Fe undergoing ramp heating at high pressure

2014 ◽  
Vol 115 (9) ◽  
pp. 093513 ◽  
Author(s):  
C. Marini ◽  
F. Occelli ◽  
O. Mathon ◽  
R. Torchio ◽  
V. Recoules ◽  
...  
Keyword(s):  
High Pressure ◽  
Phase Transitions ◽  
Time Resolved ◽  
Edge Structure ◽  
X Ray ◽  
X Ray Absorption

Time-Resolved X-Ray Absorption of An Amorphous Si Foil During Pulsed Laser Irradiation

1985 ◽  
Vol 51 ◽  
Author(s):  
Kouichi Murakami ◽  
Hans C. Gerritsen ◽  
Hedser Van Brug ◽  
Fred Bijkerk ◽  
Frans W. Saris ◽  
...  
Keyword(s):  
Laser Irradiation ◽  
Direct Evidence ◽  
Pulsed Laser ◽  
Time Resolved ◽  
Edge Structure ◽  
X Ray ◽  
Nanosecond Pulsed Laser ◽  
Amorphous Si ◽  
X Ray Absorption ◽  
Pulsed Laser Irradiation

ABSTRACTWe report time-resolved X-ray absorption and extended X-ray absorption fine structure (EXAFS) measurements on amorphous silicon under nanosecond pulsed-laser irradiation. Each measurement was performed with one laser shot in the X-ray energy range from 90 to 300 eV. An X-ray absorption spectrum for induced liquid Si (liq*Si) was first observed above an energy density of 0.17 J/cm2. It differs significantly from the spectrum for amorphous Si and characteristically shows the disappearance of the Si-L(II,III) edge structure at around 100 eV. This phenomenon is interpreted in terms of a significant reduction in the 3s-like character of the unfilled part of the conduction band of liq*Si compared to that of amorphous Si. This is the first direct evidence that liq*Si has a metallic-like electronic structure. Timeresolved EXAFS results are also discussed briefly.

scholarly journals Target current: a useful parameter for characterizing laser ablation

2017 ◽  
Vol 35 (1) ◽  
pp. 170-176 ◽  
Author(s):  
J. Krása ◽  
E. Giuffreda ◽  
D. Delle Side ◽  
V. Nassisi ◽  
D. Klír ◽  
...  
Keyword(s):  
Laser Ablation ◽  
Positive Charge ◽  
Active Phase ◽  
Nanosecond Laser ◽  
Surface Layers ◽  
Time Resolved ◽  
Target Holder ◽  
Ground Experiment ◽  
A Current ◽  
Nanosecond Laser Radiation

AbstractA current flowing between the ground and target exposed to the nanosecond laser radiation is analyzed to complete characteristics of laser ablation. Three phases of the target current are distinguished. During the ignition phase, the electron emission is driven by the laser pulse and the positive charge generated on the target is balanced by electrons coming from the ground through the target holder. At post-pulse times, a peaked waveform of the target current is typical for the active phase of the plasma and can give information on the material composition of the ablated surface layers. The afterglow phase is determined by a current of electrons flowing from the target to the ground. Experiment shows that the time-resolved target current is very sensitive to the actual composition of the surface layer of irradiated target and laser parameters.

Time-resolved XAFS measurement using quick-scanning techniques at BSRF

2017 ◽  
Vol 24 (3) ◽  
pp. 674-678 ◽  
Author(s):  
Shengqi Chu ◽  
Lirong Zheng ◽  
Pengfei An ◽  
Hui Gong ◽  
Tiandou Hu ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
High Energy ◽  
High Energy Resolution ◽  
Double Crystal ◽  
Time Resolved ◽  
Edge Structure ◽  
X Ray ◽  
Double Crystal Monochromator ◽  
Good Signal ◽  
X Ray Absorption

A new quick-scanning X-ray absorption fine-structure (QXAFS) system has been established on beamline 1W1B at the Beijing Synchrotron Radiation Facility. As an independent device, the QXAFS system can be employed by other beamlines equipped with a double-crystal monochromator to carry out quick energy scans and data acquisition. Both continuous-scan and trapezoidal-scan modes are available in this system to satisfy the time scale from subsecond (in the X-ray absorption near-edge structure region) to 1 min. Here, the trapezoidal-scan method is presented as being complementary to the continuous-scan method, in order to maintain high energy resolution and good signal-to-noise ratio. The system is demonstrated to be very reliable and has been combined with in situ cells to carry out time-resolved XAFS studies.

Soft X-ray excited colour-centre luminescence and XANES studies of calcium oxide

2007 ◽  
Vol 85 (10) ◽  
pp. 853-858 ◽  
Author(s):  
JY Peter Ko ◽  
Franziskus Heigl ◽  
Yun Mui Yiu ◽  
Xing-Tai Zhou ◽  
Tom Regier ◽  
...  
Keyword(s):  
Calcium Oxide ◽  
Density Functional ◽  
X Rays ◽  
Colour Centre ◽  
Time Resolved ◽  
Edge Structure ◽  
Colour Centres ◽  
X Ray ◽  
Optical Luminescence ◽  
X Ray Absorption

In this study, we show that colour centres can be produced by irradiating calcium oxide with soft X-rays from a synchrotron radiation source. Using the X-ray excited optical luminescence (XEOL) technique, two colour centres, F-centre, and F+-centre can be identified. These colour centres emit photons at characteristic wavelengths. In addition, by performing time-resolved XEOL (TRXEOL), we are able to reveal timing and decay characteristics of the colour centres. We also present X-ray absorption near-edge structure (XANES) spectra collected across oxygen K-edge, calcium L3,2-edge, and calcium K-edge. Experimental results are compared with density functional theory (DFT) calculations.Key words: calcium oxide, colour centre, synchrotron, X-ray excited optical luminescence, X-ray absorption near-edge structure.

Picosecond and femtosecond X-ray absorption spectroscopy of molecular systems

2010 ◽  
Vol 66 (2) ◽  
pp. 229-239 ◽  
Author(s):  
Majed Chergui
Keyword(s):  
Absorption Spectroscopy ◽  
Structural Dynamics ◽  
Intramolecular Electron Transfer ◽  
Time Resolved ◽  
Edge Structure ◽  
X Ray ◽  
Molecular Systems ◽  
Recent Developments ◽  
Amorphous Media ◽  
X Ray Absorption

The need to visualize molecular structure in the course of a chemical reaction, a phase transformation or a biological function has been a dream of scientists for decades. The development of time-resolved X-ray and electron-based methods is making this true. X-ray absorption spectroscopy is ideal for the study of structural dynamics in liquids, because it can be implemented in amorphous media. Furthermore, it is chemically selective. Using X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) in laser pump/X-ray probe experiments allows the retrieval of the local geometric structure of the system under study, but also the underlying photoinduced electronic structure changes that drive the structural dynamics. Recent developments in picosecond and femtosecond X-ray absorption spectroscopy applied to molecular systems in solution are reviewed: examples on ultrafast photoinduced processes such as intramolecular electron transfer, low-to-high spin change, and bond formation are presented.

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