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HREM STUDY OF left brace 100 right brace FERROELECTRIC DOMAIN WALLS IN POTASSIUM NIOBATE.

摘要：
High-resolution elecron microscope observations of the width and surface roughness of left brace 100 right brace ferroelectric domain walls are reported for orthorhombic potassium niobate. Both charged/coherent and uncharged/incoherent segments were identified along a single wall, with associated apparent changes in wall thickness.
作者：
Bursill L. A.;Peng Ju Lin;Feng Duan
刊名：
Philosophical Magazine A Physics of Condensed Matter Structure Defects and Mechanical Properties
在线出版时间：
1983

Observation of dislocations and subboundaries in the optically active crystal Bi12GeO20 with reflection birefringence topography

摘要：
The birefringence topography of a Bi12GeO20 single crystal which has a strong natural optical activity is presented. The natural optical activity of the crystal may be completely compensated by reflection polarised light microscopy so that the birefringence images of dislocations and subboundaries are observed. The Burgers' vectors of dislocations were found to be of the types 1/2 〈1 1 1〉, 〈1 0 0〉 and 〈1 1 0〉 and dislocations which form subboundaries are also of these types. © 1985 Chapman and Hall Ltd.
作者：
Xu Xiu-Ying;Feng Duan
刊名：
Journal of Materials Science
在线出版时间：
1985

TEM study of phases and domains in NaNbO3 at room temperature

摘要：
It is found with TEM that there is a new phase, called M phase, coexisting with the normal P and Q phases at room temperature. All kinds of ferroelectric domains in the Q phase and antiferroelectric domains in the P phase are observed. They are in good agreement with the results given by the symmetry theory on domains and domain wall orientations in the ordered phase. Translation domain walls (TDWs) are also observed in the P phase as well as in the Q phase. The translation vector was determined as [100]p (here p means pseudocubic unit cell). In addition, the effect of translation domain walls on electron diffraction is reported and interpreted theoretically. It is concluded that NaNbO3 (NN) is a heterogeneus system both in phases and in domains at room temperature. Copyright © 1988 WILEY‐VCH Verlag GmbH & Co. KGaA
作者：
Chen Jun;Feng Duan
刊名：
Physica Status Solidi A
在线出版时间：
1988

In situ TEM studies of para—ferro phase transitions in NaNbO3

摘要：
It is found from TEM observations in NaNbO3 crystals that the phase transition series from the P phase is P—R1—R2—S and that one, related to the Q phase is Q—Q1—Q2—S. It is shown that the R phase is composed of two subphases R1 and R2. The main difference between R1 and R2 is that the η values corresponding to these two phases in the superlattice spots [1/2, 1/2 ± η1/2, 0]* are 1/4 and 1/6, respectively. But the η values in the superlattice spots [1/2 ± η 1/2, 0]* corresponding to the Q1 and Q2 phases are 0 and 1/3, respectively. The main soft mode of the transition from phase S to R2 is determined as the zone boundary transverse optical mode Σ2 with wave vector q equal to [1/2, ξ, 0]*. The appearance of a superlattice spot at [1/2, 1/2, 0]* shows that the mode characterizing the tilt of octahedra is also softened due to mode—mode coupling. Copyright © 1988 WILEY‐VCH Verlag GmbH & Co. KGaA
作者：
Chen Jun;Feng Duan
刊名：
Physica Status Solidi A
在线出版时间：
1988

Direct observation of α–β phase transition in KNbW2O9 by transmission electron microscopy

摘要：
KNbW2O9 crystal with the hexagonal tungsten bronze structure is studied by TEM and electron diffraction. It is shown that KNbW2O9 has a well‐marked superstructure with tripling and doubling of unit cell dimensions along a and c, respectively. A kind of “extended antiphase boundaries” with certain width is observed in the crystals below the β → α phase transition temperature (T < 570 °C). The structure of these boundary layers may be similar to or equivalent to the structure of the high temperature α phase. These act as prefabricated nuclei for the α phase. The β → α phase transition proceeds simply by the extending of these boundary layers. There is a coexistence of the α and β phase; the phase transition is of first order. Copyright © 1988 WILEY‐VCH Verlag GmbH & Co. KGaA
作者：
Tao Ye;Hu Mei\u2010Shen;Feng Duan
刊名：
Physica Status Solidi A
在线出版时间：
1988

HREM study of defects in P ⁺ implanted Si

摘要：
By means of cross-section transmission electron microscopy, the microstructures and defects in P ⁺ implanted Si crystals are investigated. P ⁺ implantation with energy of 150 kev and dose of about 1×10 ¹⁵ cm ^-2 was done at room temperature. It is found that there exist an amorphous layer 110 nm below the incident surface of specimen with thickness of about 100 nm, and two imperfect layers which are full of defects located symmetrically on each side of the amorphous layer. {111} stacking faults and stacking fault tetrahedra are found near the amorphous layer, and {311} defects are away from the layer. The interface between the amorphous and the imperfect layers are rough. Some other microdefects are found to be randomly distributed in these two layers. But the crystalline substrate still remains perfect.
作者：
Yan Yong;Li Qi;Feng Duan;Sun Huiling;Wang Peida
刊名：
Pan Tao Ti Hsueh Pao Chinese Journal of Semiconductors
在线出版时间：
1989

Crystallographic shear planes and stacking disorders in perovskites KNbO3 and NaNbO3

摘要：
The crystallographic shear planes and stacking faults with orientations parallel to the {100} and {111} pseudocubic lattice planes are observed in perovskite crystals by means of TEM. The translation vector is determined as 〈110〉/2 for the crystallographic planes, while the stacking disorder is just the planar faults at which the stacking order of the corner‐connected octahedra in the {111} plane are misarranged to form the so‐called face‐sheared octahedra. The existence of such two kinds of planar defects indicates that the transition or alkali metal atoms can easily migrate due to the large concentrations of oxygen vacancies in the perovskite at sufficiently high temperature. Copyright © 1989 WILEY‐VCH Verlag GmbH & Co. KGaA
作者：
Chen Jun;Feng Duan
刊名：
Physica Status Solidi A
在线出版时间：
1989

TEM study of crystallization of amorphous layer in Er ⁺ implanted Si

摘要：
Variable temperature observations by cross-section transmission electron microscope and high resolution electron microscope images show that an amorphous layer is formed after an Er ⁺ (150 keV, 1 × 10 ¹⁵ cm ^-2 ) implanting into crystalline silicon. During thermal annealing, the amorphous layer is recrystallized into polysilicon layer through solid-phase epitaxial regrowth from the amorphous-crystalline interface and through the nucleation in the amorphous layer. There are a lot of twin boundaries and stacking faults in the recrystallized grains.
作者：
Yan Yong;Wang Peida;Hu Meisheng;Sun Huiling;Li Qi;Feng Duan
刊名：
Pan Tao Ti Hsueh Pao Chinese Journal of Semiconductors
在线出版时间：
1990

Amorphous silicon periodic and quasiperiodic superlattices

摘要：
Amorphous semiconductors have been entering an exciting new field of 'superlattices' in recent years. This new class of semiconducting materials, with very interesting properties, can be synthesized by alternate ultrathin layers of amorphous materials. In this paper we report the realization of amorphous silicon (a-Si:H) superlattices composed either of a-Si:H/a-SiNx:H or of a-Si:H/a-SiCx:H ultrathin layers. The results of low angle X-ray diffraction spectra and cross-section TEM photographs show that the most of the structures have sharp and smooth interfaces better than 5 A. A variety of new optical and electrical phenomena, such as the blue shift of optical and electronic gaps, space charge doping effect and a large persistent photo-conductivity, have been observed. Particularly we use the wavelength differential absorption spectra to identify the optical transition between the sub-bands in a-Si:H quantum wells. It is direct experimental evidence to verify the quantum size effect in amorphous semiconductor superlattices. A comparison is also made between periodic and quasiperiodic a-Si:H superlattices. The novel characters of quasiperiodic superlattices in the reciprocal lattice space are very different from the periodic one. The motivation for this study stems partly from the problem of one-dimensional quasiperiodic potentials and also from the new concept of 'quasicrystals'. The electronic transport properties of this 1-D quasiperiod amorphous semiconductor superlattices are also very interesting.
作者：
Chen Kunji;Du Jiafang;Li Zhifeng;Xu Jun;Jiang Jiangong;Feng Duan
刊名：
Vacuum
在线出版时间：
1991

Quasiperiodic metallic multilayers

摘要：
Quasiperiodic (Fibonacci sequence) Nb/Cu, Cu/Ti and Ta/Al metallic multilayers were fabricated by magnetron sputtering. The microstructures of these multilayers were investigated by means of X-ray and electron diffractions, TEM, Auger spectroscopy and light scattering. The self-similarity of the reciprocal lattice is approximately satisfied. The possible applications of the high-Z/low-Z quasiperiodic metallic multilayers as the optical elements at near normal incidence angle in the case of high photon energy in the soft X-ray region are discussed. Both theoretical and experimental studies on a new class of quasiperiodic structure are reported. © 1993.
作者：
Jiang S. S.;Hu A.;Peng R. W.;Feng D.
刊名：
Journal of Magnetism and Magnetic Materials
在线出版时间：
1993