Dipolar Measurements of Hydrogen in Amorphous Silicon

1992 ◽  
Vol 258 ◽  
Author(s):  
P. Hari ◽  
P.C. Taylor ◽  
R.A. Street
Keyword(s):  
Amorphous Silicon ◽  
Pulse Sequence ◽  
Lattice Relaxation ◽  
Dipolar Interaction ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Discharge System ◽  
Spin Lattice ◽  
Boron Doped ◽  
Foil Substrate

ABSTRACTThe dipolar interaction of hydrogen (∼ 10 at. %) in boron-doped amorphous silicon has been studied using the Jeener-Broekaert pulse sequence. The sample was prepared on an Al foil substrate at a temperature of 230°C using a standard glow discharge system (operating at 1 W rf power). The diborane/silane ration was 10-4. The same sample was removed from the Al substrate using dilute hydrochloric acid. The Jeener-Broekaert pulse sequence consists of three pulses: π/2|x′ – τ1 – π/4|y′ – τ2 – π/4|y′ – echo. We measured T1D, the dipolar spin lattice relaxation time, for τ1 = 82 μs, τ1 = 100 μs and τ1 = 50 μs at 299°K. The value of τ1D was found to be independent of τ1. At 335°K we found τ1D to be much longer than at room temperature. The values of τ1D at 299 K, 314 K and 335 K are, respectively, 0.7 ms, 1.2 ms and 1.8 ms. From the data we estimate an activation energy for microscopic motion to be ∼ 0.2 eV.

Change of Spin-Lattice Relaxation Time with Light Soaking for Defects in Hydrogenated Amorphous Silicon

1998 ◽  
Vol 37 (Part 1, No. 10) ◽  
pp. 5470-5473
Author(s):  
Wei-Chi Lai ◽  
Chun-Yen Chang ◽  
Meiso Yokoyama ◽  
Jen-Dar Guo ◽  
Jian-Shihn Tsang ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Amorphous Silicon ◽  
Hydrogenated Amorphous Silicon ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Spin Lattice Relaxation Time ◽  
Spin Lattice ◽  
Hydrogenated Amorphous

Dipolar Order and Spin-Lattice Relaxation in a Liquid Entrapped into Nanosize Cavities

2011 ◽  
Vol 66 (12) ◽  
pp. 779-783 ◽  
Author(s):  
Gregory Furman ◽  
Shaul Goren
Keyword(s):  
Relaxation Time ◽  
Pulse Sequence ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Local Fields ◽  
Spin Lattice Relaxation ◽  
Quasi Equilibrium ◽  
Cavity Size ◽  
Spin Lattice ◽  
Dipolar Order

It was shown that by means of the two-pulse sequence, the spin system of a liquid entrapped into nanosize cavities can be prepared in quasi-equilibrium states of high dipolar order, which relax to thermal equilibrium with the molecular environment with a relaxation time T1d. Measurements of the inverse dipolar temperature and spin-lattice relaxation time in the local fields provide an important information about the cavity size V, its shape F, and orientation θ (with respect to the external magnetic field) of the nanopores.

scholarly journals Nmr Study of Ortho-Molecular Hydrogen in Hydrogenated Amorphous Silicon

1999 ◽  
Vol 557 ◽  
Author(s):  
Tining Su ◽  
P.C. Taylor ◽  
Shenlin Chen ◽  
R.S. Crandall ◽  
A.H. Mahan
Keyword(s):  
Relaxation Time ◽  
Amorphous Silicon ◽  
Hydrogen Concentration ◽  
Molecular Hydrogen ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Spin Lattice Relaxation Time ◽  
Spin Lattice ◽  
Hydrogen Molecules

AbstractA Jeener-Broekaert three-pulse sequence is used to investigate ortho-molecular hydrogen (o-H2) in device quality amorphous silicon films prepared by plasma enhanced chemical vapor deposition (PECVD) and hot wire CVD (HWCVD). For the PECVD sample, the concentration of hydrogen molecules is ~ 11% of the total hydrogen concentration, one order of magnitude larger than that inferred from spin-lattice relaxation time measurements (~1%). Hence, most of the hydrogen molecules do not serve as effective relaxation centers. For HWCVD samples with ~3 to 4% hydrogen and very low void densities, the concentrations of hydrogen molecules are ~1% of the total hydrogen concentration. In these samples, spin-lattice relaxation measurements for bonded hydrogen indicate that the concentration of hydrogen molecules that contribute to spin-lattice relaxation is at most 0.1% of the total hydrogen concentration. Spin-lattice relaxation time (T1) measurements of ortho-molecular hydrogen indicate two very different T1's. The longer T1 is ~ 0.6 s, possibly due to an electric quadrupole-quadrupole (EQQ) interaction between o-H2 molecules and, the shorter T1 is ~ 3 ms, very close to that calculated for a two-phonon Raman process for rotating o-H2.

Doping Dependence of Local Hydrogen Motion in Hydrogenated Amorphous Silicon

1993 ◽  
Vol 297 ◽  
Author(s):  
P. Hari ◽  
P.C. Taylor ◽  
R.A. Street
Keyword(s):  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Local Motion ◽  
Rf Pulses ◽  
Spin Lattice ◽  
H Nmr ◽  
Boron Doped ◽  
Hydrogenated Amorphous ◽  
Diffusion Of Hydrogen

1H NMR dipolar echo measurements have been performed on a series of samples of phosphorus- and boron-doped a-Si:H. The dipolar echo sequence consists of three rf pulses followed by an echo in the form: (π/2)x - τ1 - (π /4)y - π2- (π /4)y - echo. The echo height is plotted against π2 and the slope yields the dipolar spin-lattice relaxation time (T1D). T1D is a measure of fluctuations in the local dipolar field surrounding each hydrogen atom in a-Si:H, and measurement of this quantity can be employed as a probe of hydrogen motion on a microscopic scale. The T1D measurements of 10-5 B-doped, 10-3 P-doped and undoped a-Si:H are compared to the previously measured T1D of 10-4 B-doped a-Si:H. The T1D values for 10-4B-doped, 10-4 B-doped and undoped a-Si:H are, respectively, 1.7 ms, 11 ms and 22 ms at 300 K. The T1D for 10-3 P-doped is found to be the same as for 10-5 B-doped within experimental error. These trends are similar to the variation of the macroscopic diffusion of hydrogen with respect to various doping levels, but the details of the local motion are very different from those of the macroscopic diffusion.

Pulsed Esr Studies on Microcrystalline Silicon

1998 ◽  
Vol 507 ◽  
Author(s):  
C. Malten ◽  
F. Finger ◽  
J. Müller ◽  
S. Yamasaki
Keyword(s):  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Microcrystalline Silicon ◽  
Field Sweep ◽  
Conduction Electrons ◽  
Spin Lattice ◽  
Boron Doped ◽  
Pulse Echo ◽  
Broad Feature

ABSTRACTTwo-pulse-echo field-sweep spectra of boron-doped samples show in addition to dangling bonds (DB) a very broad feature of approximately 500 G width. This feature is the sum of several lines whose relative intensities change with doping and temperature. The total intensity increases with doping. The spin-lattice relaxation time TI of the resonance at g=1.998 referred to as conduction electrons (CE) has been studied for undoped and P-doped microcrystalline silicon. The discrepancy between T1 values previously reported has been resolved and the values for CE are at least two orders of magnitude smaller than those of the DB. In undoped samples cross-relaxation between the CE and DB spin systems might explain the similar T1 values obtained for CE and DB in inversion recovery measurements.

NUCLEAR SPIN-LATTICE RELAXATION TIME IN TIN

1978 ◽  
Vol 39 (C6) ◽  
pp. C6-1215-C6-1216
Author(s):  
H. Ahola ◽  
G.J. Ehnholm ◽  
S.T. Islander ◽  
B. Rantala
Keyword(s):  
Relaxation Time ◽  
Nuclear Spin ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Spin Lattice Relaxation Time ◽  
Spin Lattice ◽  
Nuclear Spin Lattice Relaxation
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