Journal of Magnetism and Magnetic Materials. Volumes 198-199, 1 June 1999,

p-Type ZnO materials: Theory, growth, properties and devices

Image segmentation is a critical and important step in (GEographic) Object-Based Image Analysis (GEOBIA or OBIA). The final feature extraction and classification in OBIA is highly dependent on the quality of image segmentation. Segmentation has been used in remote sensing image processing since the advent of the Landsat-1 satellite. However, after the launch of the high-resolution IKONOS satellite in 1999, the paradigm of image analysis moved from pixel-based to object-based. As a result, the purpose of segmentation has been changed from helping pixel labeling to object identification. Although several articles have reviewed segmentation algorithms, it is unclear if some segmentation algorithms are generally more suited for (GE)OBIA than others. This article has conducted an extensive state-of-the-art survey on OBIA techniques, discussed different segmentation techniques and their applicability to OBIA. Conceptual details of those techniques are explained along with the strengths and weaknesses. The available tools and software packages for segmentation are also summarized. The key challenge in image segmentation is to select optimal parameters and algorithms that can general image objects matching with the meaningful geographic objects. Recent research indicates an apparent movement towards the improvement of segmentation algorithms, aiming at more accurate, automated, and computationally efficient techniques.

Segmentation for Object-Based Image Analysis (OBIA): A review of algorithms and challenges from remote sensing perspective

Abstract In the past 10 years, ZnO as a semiconductor has attracted considerable attention due to its unique properties, such as high electron mobility, wide and direct band gap and large exciton binding energy. ZnO has been considered a promising material for optoelectronic device applications, and the fabrications of high quality p-type ZnO and p–n junction are the key steps to realize these applications. However, the reliable p-type doping of the material remains a major challenge because of the self-compensation from native donor defects (V O and Zn i ) and/or hydrogen incorporation. Considerable efforts have been made to obtain p-type ZnO by doping different elements with various techniques. Remarkable progresses have been achieved, both theoretically and experimentally. In this paper, we discuss p-type ZnO materials: theory, growth, properties and devices, comprehensively. We first discuss the native defects in ZnO. Among the native defects in ZnO, V Zn and O i act as acceptors. We then present the theory of p-type doping in ZnO, and summarize the growth techniques for p-type ZnO and the properties of p-type ZnO materials. Theoretically, the principles of selection of p-type dopant, codoping method and X Zn –2V Zn acceptor model are introduced. Experimentally, besides the intrinsic p-type ZnO grown at O-rich ambient, p-type ZnO (MgZnO) materials have been prepared by various techniques using Group-I, IV and V elements. We pay a special attention to the band gap of p-type ZnO by band-gap engineering and room temperature ferromagnetism observed in p-type ZnO. Finally, we summarize the devices based on p-type ZnO materials.

RaoP-Type ZnO Materials: Theory, Growth, Properties, and Devices

With the growing research on image segmentation, it has become important to categorise the research outcomes and provide readers with an overview of the existing segmentation techniques in each category. In this paper, different image segmentation techniques applied on optical remote sensing images are reviewed. The selection of papers include sources from image processing journals, conferences, books, dissertations and thesis out of more than 3000 journals, books and online research databases available at UNB. The conceptual details of the techniques are explained and mathematical details are avoided for simplicity. Both broad and detailed categorisations of reviewed segmentation techniques are provided. The state of art research on each category is provided with emphasis on developed technologies and image properties used by them. The categories defined are not always mutually independent. Hence, their interrelationships are also stated. Finally, conclusions are drawn summarizing commonly used techniques and their complexities in application

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A review on image segmentation techniques with remote sensing perspective

In this work we demonstrate that high-energy electron beam irradiation (HEEBI) performed in air at room temperature affects remarkably the electrical, optical, and structural properties of undoped ZnO films prepared on SiO2 substrates by magnetron sputtering techniques. Hall and photoluminescence measurements revealed that the p-type conductivity was realized in HEEBI treated films with low dose of 1014 electrons/cm2 and converted to n-type conductivity with further increase in the amount of dose. X-ray photoelectron spectroscopy showed that indiffusion of Si from the substrate as well as N from the ambient into the films took place as a result of HEEBI treatment at high and low doses, respectively. X-ray diffraction analysis indicated that all as-grown films were found to have compressive stress, which was relieved to some extent by HEEBI treatment with high dose of 1016 electrons/cm2. It was also found that better crystallinity with a bigger grain size was observed in HEEBI treated ZnO films with a high...

Effect of high-energy electron beam irradiation on the properties of ZnO thin films prepared by magnetron sputtering

We investigated low-power (1.5-W), solenoid-type magnetic thin-film transformers with a Ni/sub 81/Fe/sub 19/ core for a 5-MHz drive dc-dc converter application. We used 2-/spl mu/m-thick Ni/sub 81/Fe/sub 19/ films covered by 20-/spl mu/m-thick copper coils as the core materials. The transformers fabricated in this study range in size from 3.08 mm /spl times/ 25.5 mm to 6.15 mm /spl times/ 12.75 mm. The design of the transformers was optimized by utilizing the conventional equations, a Maxwell three-dimensional field simulator, and parameters obtained from the magnetic properties of NiFe magnetic core materials. The 6.15 mm /spl times/ 12.75 mm transformers exhibit inductance (L) of 0.83 /spl mu/H, dc resistance of 2.3 /spl Omega/, coupling factor of 0.91, and gain of -1 dB at 5 MHz. These results are comparable to those reported in recent literature for various types of transformers sandwiched by more complex magnetic core materials. The calculated data obtained by using the well-known equation of L and the equivalent circuit agreed well with the high-frequency data for L and gain of the transformers.

Microfabrication and characteristics of low-power high-performance magnetic thin-film transformers

We report the preparation of Al–As codoped p-type ZnO films by rf magnetron cosputtering deposition. The p-type conductivity of the films was revealed by Hall measurements, x-ray photoelectron spectroscopy (XPS), and photoluminescence measurements after being annealed in O2. It was observed by XPS that Al content increased with increasing AlAs target power from 80 to 160 W and reached a maximum value at an AlAs target power of 160 W. Hole concentration decreased with increasing Al content. With increasing AlAs target power greater than 160 W, the samples exhibit increases in As and O contents and decreases in Al and Zn contents, which contribute to the increase in hole concentration. A high hole concentration of 2.354×1020 cm−3, a low resistivity of 2.122×10−2 Ω cm, and a Hall mobility of 0.13 cm2/V s for the films with high As content of 16.59% were obtained. XPS has also been used to address the unresolved issues related to the p-type formation mechanism of As-doped ZnO, supporting that the acceptor is ...

Characterization of Al–As codoped p-type ZnO films by magnetron cosputtering deposition

Simple, double-rectangular spiral-type thin-film inductors with an upper Ni81Fe19 core for 5 MHz drive dc–dc converter application were investigated. Copper films 10-μm-thick covered by a 3-μm-thick NiFe film were used as the coils. The inductors fabricated in this study are 2.5×3.4–3.5×5.5 mm2. The inductors developed, with a small size of 2.97×3.1 mm2, exhibit L of 1.43 μH, quality factor of 15.8, and resistance of 2.88 Ω at 5 MHz, and show results comparable to those reported in recent literature for similar inductors sandwiched by more complex magnetic core materials. An analysis of the experimental data suggests an equivalent circuit of the fabricated inductors. From the equivalent circuit analysis, C was shown to have a negligibly small effect over the frequency ranges used. The calculated data obtained from the equivalent circuit and the well-known equation of Q described the high-frequency data of the L, Q, and impedance of the inductors developed well.

Eui-Jung Yun

Papers

Effect of high-energy electron beam irradiation on the properties of ZnO thin films prepared by magnetron sputtering

Microfabrication and characteristics of low-power high-performance magnetic thin-film transformers

Characterization of Al–As codoped p-type ZnO films by magnetron cosputtering deposition

Microfabrication and characteristics of double-rectangular spiral type thin-film inductors with an upper NiFe magnetic core

Effect of high-energy electron beam irradiation on the properties of AZO thin films prepared by rf magnetron sputtering