Some Things Never Change - The Microcrystallite Story After 25 Years

1999 ◽  
Vol 5 (S2) ◽  
pp. 682-683
Author(s):  
J.M. Gibson ◽  
M.M.J. Treacy ◽  
P.M. Voyles
Keyword(s):  
Electron Microscopy ◽  
Amorphous Silicon ◽  
Recent Work ◽  
Amorphous Materials ◽  
Random Network ◽  
Structural Models ◽  
Glassy Materials ◽  
Silicon And Germanium ◽  
Crystalline Domains ◽  
Continuous Random Network

When I (JMG) began my Ph.D. studies under the supervision of Archie Howie in 1975, he was still licking his wounds over one of the very few apparently incorrect publications[l] of his career. I am proud that our recent work has shown that, far from being wrong, Archie and Lee Rudee were actually 25 years before their time. It was in the early 1970’s that electron microscopy instrumentation reached the performance level that was adequate to resolve the interplanar spacings in elemental materials, such as the semiconductors silicon and germanium. It immediately became of interest to examine the structure of amorphous silicon and germanium, in the expectation that direct imaging could resolve the old controversy between micro-crystallite and random network structural models. Porai-Koschits was the first to suggest that amorphous materials comprised extremely small crystalline domains (microcrystals), in contrast Zachariasen[2] proposed that a continuous random network was a better description of glassy materials.

The Structure of Ion-Implanted Amorphous Silicon

1998 ◽  
Vol 540 ◽  
Author(s):  
J. M. Gibson ◽  
J-Y. Cheng ◽  
P. Voyles ◽  
M.M.J. TREACY ◽  
D.C. Jacobson
Keyword(s):  
Amorphous Silicon ◽  
Network Model ◽  
Random Network ◽  
Amorphous Semiconductors ◽  
Range Order ◽  
Medium Range Order ◽  
Medium Range ◽  
Large Heat ◽  
Continuous Random Network ◽  
Ion Implanted

AbstractUsing fluctuation microscopy, we show that ion-implanted amorphous silicon has more medium-range order than is expected from the continuous random network model. From our previous work on evaporated and sputtered amorphous silicon, we conclude that the structure is paracrystalline, i.e. it possesses crystalline-like order which decays with distance from any point. The observation might pose an explanation for the large heat of relaxation that is evolved by ion-implanted amorphous semiconductors.

Defects in Amorphous Silicon

1982 ◽  
Vol 14 ◽  
Author(s):  
D. K. Biegelsen
Keyword(s):  
Amorphous Silicon ◽  
Electronic Properties ◽  
Crystalline Silicon ◽  
Random Network ◽  
Optical And Electronic Properties ◽  
Characteristic Features ◽  
Gap States ◽  
Hydrogenated Amorphous ◽  
Silicon Defects ◽  
Continuous Random Network

ABSTRACTIn this paper we argue that amorphous silicon can be treated as a relaxed continuous random network. The optical and electronic properties are controlled by localized gap states which arise from characteristic features of a disordered tetrahedrally-bonded covalent network. Experimental results are reviewed which indicate that the dominant (perhaps only) electrically-active defect in hydrogenated amorphous silicon is the topologically distinct, silicon dangling bond. Finally, we suggest that the same, disorder-related characteristics might also typify the electronic properties of some macroscopic crystalline silicon defects.

Observations of structural order in ion-implanted amorphous silicon

2001 ◽  
Vol 16 (11) ◽  
pp. 3030-3033 ◽  
Author(s):  
Ju-Yin Cheng ◽  
J. M. Gibson ◽  
D. C. Jacobson
Keyword(s):  
Electron Microscopy ◽  
Amorphous Silicon ◽  
Random Network ◽  
Dark Field ◽  
Range Order ◽  
Length Scale ◽  
Medium Range Order ◽  
Medium Range ◽  
Fluctuation Electron Microscopy ◽  
Ion Implanted

Medium-range order in ion-implanted amorphous silicon has been observed using fluctuation electron microscopy. In fluctuation electron microscopy, variance of dark-field image intensity contains the information of high-order atomic correlations, primarily in medium-range order length scale (1–3 nm). Thermal annealing greatly reduces the order and leaves a random network. It appears that the free energy change previously observed on relaxation may therefore be associated with randomization of the network. In this paper, we discuss the origin of the medium-range order during implantation, which can be interpreted as a paracrystalline state, that is, a disordered network enclosing compacts of highly topologically ordered grains on the length scale of 1–3 nm with significant strain fields.

scholarly journals Вертикальное упорядочение аморфных нанокластеров Ge в многослойных гетероструктурах a-Ge/a-Si:H

2021 ◽  
Vol 47 (12) ◽  
pp. 13
Author(s):  
Г.Н. Камаев ◽  
В.А. Володин ◽  
Г.К. Кривякин
Keyword(s):  
Electron Microscopy ◽  
Phase Composition ◽  
Amorphous Silicon ◽  
Low Frequency ◽  
Chemical Deposition ◽  
Plasma Chemical ◽  
Frequency Plasma ◽  
Germanium Layer ◽  
Silicon And Germanium ◽  
Microscopy Images

A multilayer heteronanostructure consisting of three pairs of amorphous silicon and amorphous germanium (a-Ge/a-Si:H) layers grown on a silicon substrate by low-frequency plasma-chemical deposition at temperature 225 oC was investigated. From the analysis of the Raman spectra, the phase composition of the silicon and germanium layers was determined, which showed that the layers are completely amorphous. The transmittance electron microscopy images show vertically ordered amorphous Ge nanoclusters initiated by local inhomogeneities in the first germanium layer, the lateral dimensions of which increase from the lower to the upper layer.

Formation of Large, Orientation-Controlled, Nearly Single Crystalline Si Thin Films on SiO2 Using Contact Printing of Rolled and Annealed Nickel Tapes

2003 ◽  
Vol 762 ◽  
Author(s):  
Hwang Huh ◽  
Jung H. Shin
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
High Resolution ◽  
Amorphous Silicon ◽  
Tem Analysis ◽  
Contact Printing ◽  
Single Crystalline ◽  
High Resolution Tem ◽  
Lateral Crystallization ◽  
Si Films

AbstractAmorphous silicon (a-Si) films prepared on oxidized silicon wafer were crystallized to a highly textured form using contact printing of rolled and annealed nickel tapes. Crystallization was achieved by first annealing the a-Si film in contact with patterned Ni tape at 600°C for 20 min in a flowing forming gas (90 % N2, 10 % H2) environment, then removing the Ni tape and further annealing the a-Si film in vacuum for2hrsat600°C. An array of crystalline regions with diameters of up to 20 μm could be formed. Electron microscopy indicates that the regions are essentially single-crystalline except for the presence of twins and/or type A-B formations, and that all regions have the same orientation in all 3 directions even when separated by more than hundreds of microns. High resolution TEM analysis shows that formation of such orientation-controlled, nearly single crystalline regions is due to formation of nearly single crystalline NiSi2 under the point of contact, which then acts as the template for silicide-induced lateral crystallization. Furthermore, the orientation relationship between Si grains and Ni tape is observed to be Si (110) || Ni (001)

Examination of a Polycrystalline Thin-Film Model to Explore the Relation between Probe Size and Structural Correlation Length in Fluctuation Electron Microscopy

2012 ◽  
Vol 18 (1) ◽  
pp. 241-253 ◽  
Author(s):  
M.M.J. Treacy ◽  
J.M. Gibson
Keyword(s):  
Electron Microscopy ◽  
Random Network ◽  
Voronoi Tessellation ◽  
Coherent Scattering ◽  
Specimen Thickness ◽  
Probe Size ◽  
Thin Film Model ◽  
Mean Grain Size ◽  
Fluctuation Electron Microscopy ◽  
Thin Polycrystalline

AbstractWe examine simulated electron microdiffraction patterns from models of thin polycrystalline silicon. The models are made by a Voronoi tessellation of random points in a box. The Voronoi domains are randomly selected to contain either a randomly-oriented cubic crystalline grain or a region of continuous random network material. The microdiffraction simulations from coherent probes of different widths are computed at the ideal kinematical limit, ignoring inelastic and multiple scattering. By examining the normalized intensity variance that is obtained in fluctuation electron microscopy experiments, we confirm that intensity fluctuations increase monotonically with the percentage of crystalline grains in the material. However, anomalously high variance is observed for models that have 100% crystalline grains with no imperfections. We confirm that the reduced normalized variance, V(k,R) − 1, that is associated with four-body correlations at scattering vector k, varies inversely with specimen thickness. Further, for probe sizes R larger than the mean grain size, we confirm that the reduced normalized variance obeys the predicted form given by Gibson et al. [Ultramicroscopy, 83, 169–178 (2000)] for the kinematical coherent scattering limit.

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