Structural perturbations within Ge nanocrystals in silica

2004 ◽  
Vol 84 (2) ◽  
pp. 278-280 ◽  
Author(s):  
A. Cheung ◽  
G. de M. Azevedo ◽  
C. J. Glover ◽  
D. J. Llewellyn ◽  
R. G. Elliman ◽  
...  
Keyword(s):  
Structural Perturbations ◽  
Ge Nanocrystals

Interactions of Ge Atoms with High- ê Oxide Dielectric Surfaces

2005 ◽  
Vol 879 ◽  
Author(s):  
Scott K. Stanley ◽  
John G. Ekerdt
Keyword(s):  
Oxide Layer ◽  
Photoelectron Spectroscopy ◽  
Chemical Vapor ◽  
Temperature Programmed Desorption ◽  
Tungsten Filament ◽  
X Ray ◽  
Dielectric Surfaces ◽  
Temperature Programmed ◽  
The Stability ◽  
Ge Nanocrystals

AbstractGe is deposited on HfO2 surfaces by chemical vapor deposition (CVD) with GeH4. 0.7-1.0 ML GeHx (x = 0-3) is deposited by thermally cracking GeH4 on a hot tungsten filament. Ge oxidation and bonding are studied at 300-1000 K with X-ray photoelectron spectroscopy (XPS). Ge, GeH, GeO, and GeO2 desorption are measured with temperature programmed desorption (TPD) at 400-1000 K. Ge initially reacts with the dielectric forming an oxide layer followed by Ge deposition and formation of nanocrystals in CVD at 870 K. 0.7-1.0 ML GeHx deposited by cracking rapidly forms a contacting oxide layer on HfO2 that is stable from 300-800 K. Ge is fully removed from the HfO2 surface after annealing to 1000 K. These results help explain the stability of Ge nanocrystals in contact with HfO2.

scholarly journals Structural Changes in the Acceptor Site of Photosystem II upon Ca2+/Sr2+ Exchange in the Mn4CaO5 Cluster Site and the Possible Long-Range Interactions

Biomolecules ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 371
Author(s):  
Koua
Keyword(s):  
Crystal Structure ◽  
Photosystem Ii ◽  
Long Range ◽  
Electron Acceptor ◽  
Structural Changes ◽  
Acceptor Site ◽  
Oxygen Evolving Complex ◽  
Long Range Interactions ◽  
Structural Perturbations ◽  
Oxygen Evolving

The Mn4CaO5 cluster site in the oxygen-evolving complex (OEC) of photosystem II (PSII) undergoes structural perturbations, such as those induced by Ca2+/Sr2+ exchanges or Ca/Mn removal. These changes have been known to induce long-range positive shifts (between +30 and +150 mV) in the redox potential of the primary quinone electron acceptor plastoquinone A (QA), which is located 40 Å from the OEC. To further investigate these effects, we reanalyzed the crystal structure of Sr-PSII resolved at 2.1 Å and compared it with the native Ca-PSII resolved at 1.9 Å. Here, we focus on the acceptor site and report the possible long-range interactions between the donor, Mn4Ca(Sr)O5 cluster, and acceptor sites.

scholarly journals Charge trapping and retention behaviors of Ge nanocrystals distributed in the gate oxide near the gate synthesized by low-energy ion implantation

2007 ◽  
Vol 101 (12) ◽  
pp. 124313 ◽  
Author(s):  
M. Yang ◽  
T. P. Chen ◽  
J. I. Wong ◽  
C. Y. Ng ◽  
Y. Liu ◽  
...  
Keyword(s):  
Ion Implantation ◽  
Charge Trapping ◽  
Gate Oxide ◽  
Low Energy ◽  
Ge Nanocrystals

Characterization of Ge nanocrystals in a-SiO2 synthesized by rapid thermal annealing

1999 ◽  
Vol 144-145 ◽  
pp. 697-701 ◽  
Author(s):  
W.K Choi ◽  
S Kanakaraju ◽  
Z.X Shen ◽  
W.S Li
Keyword(s):  
Thermal Annealing ◽  
Rapid Thermal Annealing ◽  
Ge Nanocrystals

Characterization and Manipulation of Exposed Ge Nanocrystals

2004 ◽  
Vol 818 ◽  
Author(s):  
I.D. Sharp ◽  
Q. Xu ◽  
C.Y. Liao ◽  
D.O. Yi ◽  
J.W. Ager ◽  
...  
Keyword(s):  
Hydrofluoric Acid ◽  
Metal Films ◽  
Silica Matrix ◽  
Size Distributions ◽  
Si Substrates ◽  
Atomic Force ◽  
Transmission Electron ◽  
Oxide Matrix ◽  
Ge Nanocrystals

AbstractIsotopically pure 70Ge and 74Ge nanocrystals embedded in SiO2 thin films on Si substrates have been fabricated through ion implantation and thermal annealing. Nanocrystals were subsequently exposed using a hydrofluoric acid etching procedure to selectively remove the oxide matrix while retaining up to 69% of the implanted Ge. Comparison of transmission electron micrographs (TEM) of as-grown crystals to atomic force microscope (AFM) data of exposed crystals reveals that the nanocrystal size distribution is very nearly preserved during etching. Therefore, this process provides a new means to use AFM for rapid and straightforward determination of size distributions of nanocrystals formed in a silica matrix. Once exposed, nanocrystals may be transferred to a variety of substrates, such as conducting metal films and optically transparent insulators for further characterization.

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