Deposition characteristics and microstructures of the high Tc superconducting Y1Ba2Cu3O7−δ thin films prepared by MOCVD

1991 ◽  
Vol 6 (4) ◽  
pp. 704-711 ◽  
Author(s):  
Sang Ho Kim ◽  
Chang Hyun Cho ◽  
Kwang Soo No ◽  
John S. Chun
Keyword(s):  
Electron Microscopy ◽  
Surface Morphology ◽  
Chemical Vapor ◽  
Zero Magnetic Field ◽  
Organic Chemical ◽  
Transmission Electron ◽  
Transformation Twins ◽  
Metal Organic ◽  
Zero Resistance ◽  
Organic Chemical Vapor Deposition

Superconducting Y1Ba2Cu3O7−δ films were prepared on the MgO (100) and SrTiO3 (100) single crystals using metal organic chemical vapor deposition (MOCVD) of β-diketone metal chelates of Y(thd)3, Ba(th)2, and Cu(thd)2. The evaporation kinetics of Y(thd)3, Ba(thd)2, and Cu(thd)2 and the ratios of deposited to evaporated mole percents of Y, Ba, and Cu cations were studied. The microstructure of Y1Ba2Cu3O7−δ films deposited using MOCVD was observed using scanning electron microscopy and transmission electron microscopy to investigate surface morphology change with the film composition and transformation twin structures. The experimental results showed that the volatility of Ba(thd)2 did not perceptively increase with decreasing evaporation pressure from 10 Torr to 5 Torr, but that of Y(thd)3 or Cu(thd)2 increased with the pressure decrease. The ratio of deposited to evaporated mole percents of Ba cation was smaller than those of Y and Cu cations. Therefore, Ba must be evaporated more than the stoichiometric amount for Y1Ba2Cu3O7−δ in order to obtain single phase Y1Ba2Cu3O7−δ films. The surface morphology of the Y1Ba2Cu3O7−δ films showed perculiar changes with slight composition changes. The transition onset and zero resistance temperatures of typical stoichiometric film deposited on MgO were 93 K and 91 K, respectively. The Y1Ba2Cu3O7−δ films had about 50 nm grain size, and most grains consisted of transformation twins. The critical current density of a film deposited on SrTiO3 was 105 A/cm2 at 77 K and zero magnetic field.

Microstructural Characterization of GaN Grown on SiC

2019 ◽  
Vol 25 (6) ◽  
pp. 1383-1393
Author(s):  
Sabyasachi Saha ◽  
Deepak Kumar ◽  
Chandan K. Sharma ◽  
Vikash K. Singh ◽  
Samartha Channagiri ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Raman Spectroscopy ◽  
Surface Morphology ◽  
Chemical Vapor ◽  
Microstructural Characterization ◽  
Organic Chemical ◽  
Nucleation Layer ◽  
Transmission Electron ◽  
Vapor Deposition Technique ◽  
Metal Organic

AbstractGaN films have been grown on SiC substrates with an AlN nucleation layer by using a metal organic chemical vapor deposition technique. Micro-cracking of the GaN films has been observed in some of the grown samples. In order to investigate the micro-cracking and microstructure, the samples have been studied using various characterization techniques such as optical microscopy, atomic force microscopy, Raman spectroscopy, scanning electron microscopy and transmission electron microscopy (TEM). The surface morphology of the AlN nucleation layer is related to the stress evolution in subsequent overgrown GaN epilayers. It is determined via TEM evidence that, if the AlN nucleation layer has a rough surface morphology, this leads to tensile stresses in the GaN films, which finally results in cracking. Raman spectroscopy results also suggest this, by showing the existence of considerable tensile residual stress in the AlN nucleation layer. Based on these various observations and results, conclusions or propositions relating to the microstructure are presented.

Ferroelectric Domain Boundaries Induced by Interface Mismatch Dislocations in BaTiO3/LaAlO3

1996 ◽  
Vol 466 ◽  
Author(s):  
Z. L. Wang ◽  
Z. R. Dai
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Ferroelectric Domain ◽  
Organic Chemical ◽  
Transmission Electron ◽  
Domain Boundaries ◽  
Metal Organic ◽  
Organic Chemical Vapor Deposition

ABSTRACTInterface microstractures of BaTiO3/LaAlO3 grown by metal-organic chemical vapor deposition (MOCVD) are studied using high-resolution transmission electron microscopy (HRTEM). Interface dislocations in BaTiO3/LaAlO3 have been shown to be directly linked with the 90° domain boundaries in BaTiO3. This association is a result of strain relief due to a phase transformation on cooling from the growth temperature. The {100} surfaces of BaTiO3 are terminated with the Ba-O layer.

Metal organic chemical vapor deposition of m-plane GaN epi-layer using a three-step approach towards enhanced surface morphology

2018 ◽  
Vol 667 ◽  
pp. 48-54
Author(s):  
Adreen Azman ◽  
Ahmad Shuhaimi ◽  
Al-Zuhairi Omar ◽  
Anas Kamarundzaman ◽  
Muhammad Imran Mustafa Abdul Khudus ◽  
...  
Keyword(s):  
Chemical Vapor Deposition ◽  
Surface Morphology ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Organic Chemical ◽  
Metal Organic ◽  
Organic Chemical Vapor Deposition ◽  
Enhanced Surface

TEM Study of MOCVD Grown InSb/GaAs Heterostructures with and without TMIn Predeposited Layers

1994 ◽  
Vol 340 ◽  
Author(s):  
L. H. Kuo ◽  
Susan Z. Hua ◽  
L. Salamanca-Riba ◽  
D. L. Partin ◽  
L. Green ◽  
...  
Keyword(s):  
Vapor Deposition ◽  
Chemical Vapor ◽  
Organic Chemical ◽  
Threading Dislocations ◽  
High Quality ◽  
Gaas Substrates ◽  
Transmission Electron ◽  
Metal Organic ◽  
Step Growth ◽  
Organic Chemical Vapor Deposition

ABSTRACTHigh quality InSb epilayers were grown on GaAs substrates by metal organic chemical vapor deposition using a two-step growth procedure involving trimethal indium (TMIn) predeposition. From transmission electron microscopy studies, we found that an interdiffusion layer of thickness of 10 Å forms at the interface when the substrate is exposed to TMIn for approximately 6 secs prior to the growth of the InSb filns. Hall mobilities up to σ 52,000 cm2/V-s were obtained at 300 K on a 2.1-μm-thick InSb heteroepitaxial film. In contrast, samples without TMIn predeposition showed polycrystallinity of the InSb films grown on single crystalline GaAs substrates. The effect. of TMNIn predeposition is to minimize the misorientation of the grains, suppress the polycrystallinity, decrease the density of threading dislocations, and increase the electron mobilities in the films. However, we found that too much TMIn predeposition gives rise t.o an intermixing layer at the InSb/GaAs interface which deteriorates the film quality. Details of the effect of the TMIn predeposition on the microstructure of InSb/GaAs with different predeposition times (zero, 6, and 12 secs) are discussed.

Pinning of 90° domain boundaries at interface dislocations in BaTiO3/LaAIO3 {100}

1996 ◽  
Vol 54 ◽  
pp. 124-125
Author(s):  
Z.-R. Dai ◽  
Z.L. Wang ◽  
X.F. Duan ◽  
J. Zhang
Keyword(s):  
Thin Films ◽  
Chemical Vapor ◽  
Organic Chemical ◽  
Epitaxial Thin Films ◽  
Transmission Electron ◽  
Domain Boundaries ◽  
Potential Applications ◽  
Metal Organic ◽  
Organic Chemical Vapor Deposition

Epitaxially grown BaTiO3 thin films have potential applications in microelectronics and integrated photonics. The ferroelectric property of this material is largely determined by the domain structure. It is believed that the structure of the substrate would have profound effect on the quality of BaTiO3 epitaxial thin films. This paper reports our studies on the pinning of 90° domain boundaries at interface dislocations.Epitaxial BaTiO3 thin films were deposited on single crystalline LaAIO3 (100) substrates at 800°C by metal-organic chemical vapor deposition (MOCVD). Cross-section specimens of the films were studied at 200 kV using an JEOL 2010 high-resolution transmission electron microscope (HRTEM).

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