Real Time Control of III-V Semiconductor Surfaces During Movpe Growth by Reflectance Anisotropy Spectroscopy

1993 ◽  
Vol 334 ◽  
Author(s):  
K. Ploska ◽  
W. Richter ◽  
F. Reinhardt ◽  
J. JÖnsson ◽  
J. Rumberg ◽  
...  
Keyword(s):  
Molecular Beam Epitaxy ◽  
Real Time ◽  
Molecular Beam ◽  
Substrate Surface ◽  
Exchange Reactions ◽  
Real Time Control ◽  
Time Resolved ◽  
Reflectance Anisotropy ◽  
Time Control ◽  
Metalorganic Molecular Beam Epitaxy

AbstractReflectance anisotropy spectroscopy (RAS) is presented as real time analytical tool for metalorganic vapourphase epitaxy (MOVPE) of III-V-semiconductors. This optical method derives its surface sensitivity from the anisotropy of surface structures. It is shown that it is possible to monitor with RAS the oxide desorption from the substrate and that the substrate surface conditions thereafter, still in the pregrowth stage, can be correlated with certain reconstructions of the (001)-surfaces of InP and GaAs. The latter is possible through simultaneous RAS and RHEED measurements during MBE (molecular beam epitaxy) or MOMBE (metalorganic molecular beam epitaxy). Characteristic spectral features are also observed for other binary or ternary III-V-semiconductors. Time resolved measurements during growth give monolayer resolution for the growth rate in the case of GaAs. In the study of heterointerface growth exchange reactions between As and P together with their corresponding reaction time constants can be monitored and conclusions for the epitaxial growth procedure can be drawn.

Optical-based Flux Monitoring of Atomic Antimony Sources for Molecular Beam Epitaxy

1995 ◽  
Vol 406 ◽  
Author(s):  
P. D. Brewer ◽  
K. P. Killeen
Keyword(s):  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Flux Measurement ◽  
Product Distribution ◽  
Effusion Cell ◽  
Real Time Control ◽  
Double Pass ◽  
Mbe Growth ◽  
Time Control ◽  
Flux Monitoring

AbstractIn this paper we discuss the use of optical-based flux monitoring (OFM) for real-time control of atomic antimony fluxes for applications in molecular beam epitaxy. Atomic antimony beams were generated using a two-zone cracking effusion cell. The product distribution of the source was characterized using a time-of-flight mass spectrometer employing resonance-enhanced laser ionization. A double-pass OFM system has been developed to monitor the atomic antimony beam that is capable of precise flux measurement during MBE growth.

Real-time control of quantum dot laser growth using reflectance anisotropy spectroscopy

2004 ◽  
Vol 272 (1-4) ◽  
pp. 143-147 ◽  
Author(s):  
U.W. Pohl ◽  
K. Pötschke ◽  
I. Kaiander ◽  
J.-T. Zettler ◽  
D. Bimberg
Keyword(s):  
Quantum Dot ◽  
Real Time ◽  
Real Time Control ◽  
Reflectance Anisotropy ◽  
Time Control ◽  
Quantum Dot Laser

Temperature Dependence of morphology of InP Films Grown by metalorganic molecular Beam Epitaxy

1993 ◽  
Vol 317 ◽  
Author(s):  
M.A. Cotta ◽  
R.A. Hamm ◽  
S.N.G. Chu ◽  
L.R. Harriott ◽  
H. Temkin
Keyword(s):  
Activation Energy ◽  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Initial Conditions ◽  
Substrate Surface ◽  
Epitaxial Films ◽  
Kinetic Roughening ◽  
A Value ◽  
Metalorganic Molecular Beam Epitaxy ◽  
Increasing Temperature

ABSTRACTTwo regimes of growth are observed for epitaxial films of InP prepared by metalorganic molecular beam epitaxy. Below a minimum growth temperature, kinetic roughening is observed. At temperatures higher than smooth morphologies are obtained. From the dependence of on the substrate Misorientation, we estimate a value of ∼0.4–0.5eV for the Schwoebel barrier. At growth temperatures higher than we observe two types of defects: large oval defects related only to the initial conditions of the substrate surface and small defects with the density strongly dependent on the growth condition. Increasing temperature above or decreasing V/III ratio, results in increased density of these defects. In addition, their density increases with an activation energy that depends on the substrate Misorientation. The origin of the oval defects is attributed to non-stoichiometric, P-defficient, clusters on the growing surface, formed either by enhanced cracking of metalorganic s on the substrate due to the presence of contaminants or by a low V/III ratio used for growth.

A Real Time Control Architecture for Continuously Managing Patients in a Care Unit

1995 ◽  
Vol 34 (05) ◽  
pp. 475-488
Author(s):  
B. Seroussi ◽  
J. F. Boisvieux ◽  
V. Morice
Keyword(s):  
Real Time ◽  
Linear Time ◽  
Treatment Plan ◽  
Control Architecture ◽  
Real Time Control ◽  
Time Representation ◽  
Time Control ◽  
Continuous Support ◽  
Definition Of ◽  
Computerized System

Abstract:The monitoring and treatment of patients in a care unit is a complex task in which even the most experienced clinicians can make errors. A hemato-oncology department in which patients undergo chemotherapy asked for a computerized system able to provide intelligent and continuous support in this task. One issue in building such a system is the definition of a control architecture able to manage, in real time, a treatment plan containing prescriptions and protocols in which temporal constraints are expressed in various ways, that is, which supervises the treatment, including controlling the timely execution of prescriptions and suggesting modifications to the plan according to the patient’s evolving condition. The system to solve these issues, called SEPIA, has to manage the dynamic, processes involved in patient care. Its role is to generate, in real time, commands for the patient’s care (execution of tests, administration of drugs) from a plan, and to monitor the patient’s state so that it may propose actions updating the plan. The necessity of an explicit time representation is shown. We propose using a linear time structure towards the past, with precise and absolute dates, open towards the future, and with imprecise and relative dates. Temporal relative scales are introduced to facilitate knowledge representation and access.

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