Improved Quality of Bulk II-VI Substrates for HgcdTe and HgZnTe Epitaxy

1994 ◽  
Vol 299 ◽  
Author(s):  
Sanghamitra Sen ◽  
John E. Stannard
Keyword(s):  
Defect Density ◽  
Substrate Material ◽  
Current Status ◽  
Large Area ◽  
Ir Detector ◽  
Lattice Matching ◽  
Research Areas ◽  
Critical Issues ◽  
Common Technique ◽  
Primary Focus

AbstractSingle crystals of CdTe or dilute alloys of Cd1−yZnyTe (y≤0.04) and CdTe1−zSez (z ≤0.04) with low defect density, high purity and large single-crystal area (>30 cm2) are required as substrates for high-quality epitaxial Hg1−xCdxTe thin films in the infrared (IR) detector industry. Bridgman or gradient freeze is the most common technique used for commercial production of these materials because of its success in producing large area substrates of good quality and reproducibility. For epitaxial growth of Hg1−xZnxTe, which has been of considerable interest in recent years as an IR detector material, the substrate of choice has been Cd0.80Zn0.20Te, for lattice matching with long wavelength Hg1−xZnxTe epitaxial layers (x = 0.13–0.14). The primary focus of this paper is on CdZnTe which is currently the preferred substrate material and most widely used for both HgCdTe and HgZnTe epitaxy. This paper reviews the current status of bulk substrate technology for IR detector applications, highlighting critical issues and essential research areas for further improvement of these materials.

Improved Quality of Bulk II-VI Substrates for HgCdTe and HgZnTe Epitaxy

1993 ◽  
Vol 302 ◽  
Author(s):  
Sanghamitra Sen ◽  
John E. Stannard
Keyword(s):  
Defect Density ◽  
Substrate Material ◽  
Current Status ◽  
Large Area ◽  
Ir Detector ◽  
Lattice Matching ◽  
Research Areas ◽  
Critical Issues ◽  
Common Technique ◽  
Primary Focus

ABSTRACTSingle crystals of CdTe or dilute alloys of Cdl−y ZnyTe (y ≤ 0.04) and CdTel−zSez (z ≤ 0.04) with low defect density, high purity and large single-crystal area (>30 cm2) are required as substrates for high-quality epitaxial Hgl−xCdxTe thin films in the infrared (IR) detector industry. Bridgman or gradient freeze is the most common technique used for commercial production of these materials because of its success in producing large area substrates of good quality and reproducibility. For epitaxial growth of Hg1−xZnxTe, which has been of considerable interest in recent years as an IR detector material, the substrate of choice has been Cd0.80Zn0.20Te, for lattice matching with long wavelength Hg1−xZnxTe epitaxial layers (x = 0.13–0.14). The primary focus of this paper is on CdZnTe which is currently the preferred substrate material and most widely used for both HgCdTe and HgZnTe epitaxy. This paper reviews the current status of bulk substrate technology for IR detector applications, highlighting critical issues and essential research areas for further improvement of these materials.

Growth of Large-Diameter CdZnTe and CdTeSe Boules for Hg1−xCdxTe Epitaxy: Status and Prospects

1989 ◽  
Vol 161 ◽  
Author(s):  
S. Sen ◽  
S.M. Johnson ◽  
J.A. Kiele ◽  
W.H. Konkel ◽  
J.E. Stannard
Keyword(s):  
Single Crystal ◽  
Defect Density ◽  
Large Diameter ◽  
Cylindrical Body ◽  
Growth Conditions ◽  
Grain Structure ◽  
Current Status ◽  
Conductive Heat ◽  
Large Area ◽  
Ir Detector

ABSTRACTSingle crystals of CdTe or dilute alloys of Cd1−yZnyTe (y ≤ 0.04) and CdTe1−zSez (z ≤ 0.04) with low defect density and large single-crystal area (>30 cm2) are required as substrates for high-quality epitaxial Hg1−xCdxTe thin films in the infrared (IR) detector industry. Bridgman or gradient freeze has been the most common current technique used for growing these materials. This paper reviews the current status and the evolution at SBRC of one variation of the Bridgman technique, viz., vertical-modified Bridgman (VMB), for producing large-area substrates with excellent uniformity and reproducibility. CdTe, Cd1−yZnyTe (y ≤ 0.04) and CdTe1−zSez (z ≤ 0.04) boules of 5-to 7.5-cm diameter have been grown unseeded in the present version of the VMB growth system. In general, under optimum growth conditions, the boules have the smallest grain structure (several grains) at the tip end with enhancement of grain selection as the cylindrical body of the boule is approached, resulting in one predominant and large grain occupying 70 to 80 percent of the entire boule volume; {111}-oriented Cd1−yZnyTe and CdTe1−zSez substrates with single-crystal areas as large as 50 to 60 cm2 have been obtained from these boules. Crystal quality characterized by x-ray rocking curve, IR transmission (2.5 to 20 µm), low-temperature photoluminescence, and Hall-effect measurements as a function of temperature, showed a strong correlation with the starting material quality (especially that of elemental Te and Se). Analyses of the thermal history during growth reveals that the presence of the ampoule (with charge) increases the temperature inside the furnace by 10 to 15 degrees. The temperature gradient at the tip was measured to be 8 to 10°C/cm and it dropped to 4 to 5°C/cm beyond 2.5 cm from the tip - where rapid enhancement of grain selection takes place in most boules. The effect of this temperature rise on the initial crystallization near the tip of a boule can be explained from the numerical thermal model that was developed for the growth process with radiative and conductive heat transfer included and using a temperature profile similar to that existing in the actual growth furnace. Conditions for maximizing the fraction solidifying with a slightly convex interface, hence maximizing the single-crystal yield are discussed.

scholarly journals Solar Cells for Indoor Applications: Progress and Development

Polymers ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1338
Author(s):  
Swarup Biswas ◽  
Hyeok Kim
Keyword(s):  
Solar Cells ◽  
Low Cost ◽  
Environmental Stability ◽  
Current Status ◽  
Background Information ◽  
Light Sources ◽  
Large Area ◽  
Dye Sensitized ◽  
Low Intensity ◽  
Critical Issues

The Internet of things (IoT) has been rapidly growing in the past few years. IoT connects numerous devices, such as wireless sensors, actuators, and wearable devices, to optimize and monitor daily activities. Most of these devices require power in the microwatt range and operate indoors. To this end, a self-sustainable power source, such as a photovoltaic (PV) cell, which can harvest low-intensity indoor light, is appropriate. Recently, the development of highly efficient PV cells for indoor applications has attracted tremendous attention. Therefore, different types of PV materials, such as inorganic, dye-sensitized, organic, and perovskite materials, have been employed for harvesting low-intensity indoor light energy. Although considerable efforts have been made by researchers to develop low-cost, stable, and efficient PV cells for indoor applications, Extensive investigation is necessary to resolve some critical issues concerning PV cells, such as environmental stability, lifetime, large-area fabrication, mechanical flexibility, and production cost. To address these issues, a systematic review of these aspects will be highly useful to the research community. This study discusses the current status of the development of indoor PV cells based on previous reports. First, we have provided relevant background information. Then, we have described the different indoor light sources, and subsequently critically reviewed previous reports regarding indoor solar cells based on different active materials such as inorganic, dye-sensitized, organic, and perovskite. Finally, we have placed an attempt to provide insight into factors needed to further improve the feasibility of PV technology for indoor applications.

Critical issues and current status of SiC/SiC composites for fusion

2000 ◽  
Vol 283-287 ◽  
pp. 128-137 ◽  
Author(s):  
A. Hasegawa ◽  
A. Kohyama ◽  
R.H. Jones ◽  
L.L. Snead ◽  
B. Riccardi ◽  
...  
Keyword(s):  
Current Status ◽  
Critical Issues ◽  
Sic Composites

scholarly journals Current status and future directions of cardiac rehabilitation program: a review of the literature

2019 ◽  
Vol 2 (2) ◽  
pp. 59-68
Author(s):  
Sutantri Sutantri
Keyword(s):  
Cardiac Rehabilitation ◽  
Good Health ◽  
Rehabilitation Program ◽  
Current Status ◽  
Participation Rates ◽  
Risk Factor Management ◽  
Research Areas ◽  
The Usa ◽  
Cardiac Illness ◽  
New Research

One of the effective treatments for patients recovering from acute cardiac illness or surgery is cardiac rehabilitation (CR). CR has proven to be effective to reduce mortality, morbidity, and also to improve the quality of life. The purpose of this review is to present the current status of CR program worldwide as well as to identify a potential approach for further investigation. Literature searching of electronic databases was conducted in several databases including CINAHL, MEDLINE, PsycINFO, and EMBASE, and Google Scholar. CR aims to restore patients with CVD to a state of good health. Each country has different approach in the provision and organization of CR as well as the allocation of resources, which depends on their health policies and politics. The indications for CR also differ between countries, but traditionally CR has been used following acute myocardial infarction (MI). CR programs have been divided into three phases of progression. Hospital-based or supervised site-based programs have been known as the most common model of CR in most countries. The core components of CR include patient assessment, nutritional counselling, exercise training, physical activity counselling, weight management, tobacco cessation, aggressive coronary risk-factor management, and psychosocial management. Despite the apparent benefits of CR in patients with CVD, these programs remain largely underused. The participation rates in the USA, Australia, and Europe are low, estimated at 10-30%. New research areas that explore new ways of CR delivery to improve referral and participation rates are essential.

scholarly journals On reconstruction of the coefficient in complex Helmholtz’s equation

2021 ◽  
Vol 2056 (1) ◽  
pp. 012015
Author(s):  
M Malovichko ◽  
A Orazbayev ◽  
Yu Kloss ◽  
N Khokhlov
Keyword(s):  
Helmholtz Equation ◽  
Waveform Inversion ◽  
Theory Of Elasticity ◽  
Two Dimensions ◽  
Seismic Exploration ◽  
Research Areas ◽  
Full Waveform ◽  
Early Results ◽  
Fast Solution ◽  
Primary Focus

Abstract This note summarizes some preliminary results on the fast solution of the coefficient inverse problem for the Helmholtz equation, given measured pressure in a set of observation points. The Helmholtz equation is the model PDE for the harmonic problem of the linear theory of elasticity, and this work is a move in that direction. The problem has been the primary focus for several research areas, most notably seismic exploration. Still, practical problems are very challenging because they are non-linear and large. In this paper, we develop a novel numerical method for seismic full-waveform inversion based on Newton iterations. Its distinctive future is that it does not require the Jacobian of the target functional. Thus, in certain scenarios, it will perform only a fraction of computations comparing to the conventional Gauss-Newton algorithm. We present some early results on the Helmholtz equation in two dimensions.

Critical Issues in Requirements Engineering Education

2017 ◽  
pp. 1953-1976
Author(s):  
Rafia Naz Memon ◽  
Rodina Ahmad ◽  
Siti Salwah Salim
Keyword(s):  
Engineering Education ◽  
Requirements Engineering ◽  
Current Status ◽  
Development Projects ◽  
Teaching Approaches ◽  
Critical Issues ◽  
Research Problems ◽  
Software Engineers ◽  
The University ◽  
Difficult Subject

Requirements Engineering (RE) is the most crucial process within software development projects. In order to prepare skilled requirements engineers, Requirements Engineering Education (REE) needs to be provided to students at the university level before they become software engineers and part of the workforce. However, RE is considered the most difficult subject within the software engineering curriculum for students to learn and for lecturers to teach due to its uncertain nature. This chapter examines the current and potential areas for research within REE. It first presents the current status of REE provided in universities and the REE problems reported in the literature that lead us to the potential research problems in REE. The REE teaching approaches proposed by researchers are then elaborated. The proposed approaches are mapped back to address the REE problems. The chapter closes with recommended directions for future REE research.

scholarly journals Patient Derived Chicken Egg Tumor Model (PDcE Model): Current Status and Critical Issues

Cells ◽  
2019 ◽  
Vol 8 (5) ◽  
pp. 440 ◽  
Author(s):  
Aoi Komatsu ◽  
Kotaro Matsumoto ◽  
Tomoki Saito ◽  
Manabu Muto ◽  
Fuyuhiko Tamanoi
Keyword(s):  
Cancer Patients ◽  
Chorioallantoic Membrane ◽  
Tumor Model ◽  
Tumor Formation ◽  
Current Status ◽  
Cam Assay ◽  
Chicken Egg ◽  
Critical Issues ◽  
Chicken Eggs ◽  
Chorioallantoic Membrane Assay

Chorioallantoic membrane assay (CAM assay) using fertilized chicken eggs has been used for the study of tumor formation, angiogenesis and metastasis. Recently, there is growing realization that this system provides a valuable assay for a patient-derived tumor model. Several reports establish that tumor samples from cancer patients can be used to reproduce tumor in the chicken egg. High transplantation efficiency has been achieved. In this review, we discuss examples of transplanting patient tumors. We then discuss critical issues that need to be addressed to pursue this line of experiments. The patient-derived chicken egg model (PDcE model) has an advantage over other models in its rapid tumor formation. This raises the possibility that the PDcE model is valuable for identifying optimum drug for each individual patient.

scholarly journals Molecular Tools for Detection and Identification of Paracoccidioides Species: Current Status and Future Perspectives

2020 ◽  
Vol 6 (4) ◽  
pp. 293 ◽  
Author(s):  
Breno Gonçalves Pinheiro ◽  
Rosane Christine Hahn ◽  
Zoilo Pires de Camargo ◽  
Anderson Messias Rodrigues
Keyword(s):  
Current Status ◽  
Large Area ◽  
Mycelial Form ◽  
Dimorphic Fungi ◽  
Laboratory Techniques ◽  
Detection And Identification ◽  
Paracoccidioides Spp ◽  
Taxonomic Changes ◽  
Immunological Assays ◽  
Mycotic Disease

Paracoccidioidomycosis (PCM) is a mycotic disease caused by the Paracoccidioides species, a group of thermally dimorphic fungi that grow in mycelial form at 25 °C and as budding yeasts when cultured at 37 °C or when parasitizing the host tissues. PCM occurs in a large area of Latin America, and the most critical regions of endemicity are in Brazil, Colombia, and Venezuela. The clinical diagnosis of PCM needs to be confirmed through laboratory tests. Although classical laboratory techniques provide valuable information due to the presence of pathognomonic forms of Paracoccidioides spp., nucleic acid-based diagnostics gradually are replacing or complementing culture-based, biochemical, and immunological assays in routine microbiology laboratory practice. Recently, taxonomic changes driven by whole-genomic sequencing of Paracoccidioides have highlighted the need to recognize species boundaries, which could better ascertain Paracoccidioides taxonomy. In this scenario, classical laboratory techniques do not have significant discriminatory power over cryptic agents. On the other hand, several PCR-based methods can detect polymorphisms in Paracoccidioides DNA and thus support species identification. This review is focused on the recent achievements in molecular diagnostics of paracoccidioidomycosis, including the main advantages and pitfalls related to each technique. We discuss these breakthroughs in light of taxonomic changes in the Paracoccidioides genus.

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