Pub Date : 2002-10-01DOI: 10.1177/1524511X02043537
Y. Ma, W. L. Wang, K. Liao, C. Kong
The surface barriers at the neck of nano-ZnO gas elements are expressed in terms of the electrical potential inside a cylinder, and then the resistance, the sensitivity, and the grain-size effect are discussed. It is shown that the sensing property of nano-ZnO gas elements is influenced by the microstructural features, such as the grain size, the geometry, and the connectivity between grains. The difference between the neck-controlled sensitivity and the neck-grain-boundary- controlled sensitivity is large when the width of the depletion layer at the neck in air is comparable with the neck radius. It implies that although the grain-boundary resistance may be much smaller than the neck resistance it cannot be neglected. It is suggested that the decreasing of the ratio between the numbers of grain boundaries and necks is a possible approach to the development of nano-ZnO gas sensors with a high sensitivity.
{"title":"Study on Sensitivity of Nano-Grain ZnO Gas Sensors","authors":"Y. Ma, W. L. Wang, K. Liao, C. Kong","doi":"10.1177/1524511X02043537","DOIUrl":"https://doi.org/10.1177/1524511X02043537","url":null,"abstract":"The surface barriers at the neck of nano-ZnO gas elements are expressed in terms of the electrical potential inside a cylinder, and then the resistance, the sensitivity, and the grain-size effect are discussed. It is shown that the sensing property of nano-ZnO gas elements is influenced by the microstructural features, such as the grain size, the geometry, and the connectivity between grains. The difference between the neck-controlled sensitivity and the neck-grain-boundary- controlled sensitivity is large when the width of the depletion layer at the neck in air is comparable with the neck radius. It implies that although the grain-boundary resistance may be much smaller than the neck resistance it cannot be neglected. It is suggested that the decreasing of the ratio between the numbers of grain boundaries and necks is a possible approach to the development of nano-ZnO gas sensors with a high sensitivity.","PeriodicalId":246239,"journal":{"name":"Journal of Wide Bandgap Materials","volume":"40 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129661068","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-10-01DOI: 10.1177/1524511X02043541
M. West, M. Prelas, R. Tompson, A. Khomich
The principal author reports here the main elements of work performed as part of his 1999 Ph.D. dissertation (Matthew Keith West, ''Diffusion of Sulfur into Natural Diamond: Characterization and Applications in Radiation Detection''. Ph.D. Dissertation, University of Missouri-Columbia, USA (1999)). In this study a Field Enhanced Diffusion with Optical Activation (FEDOA) reactor was constructed, tested, and employed to diffuse sulfur and sodium into polished, natural diamond plates. Various chemical sources of sulfur were used for diffusion from the gaseous, liquid, and solid phases. Diffusion coefficients in the range of 10 � 15 cm 2 /s to 10 � 14 cm 2 /s for temperatures 450-1050 � C, have been calculated for sulfur from concentration profiles determined from secondary ion mass spectroscopy (SIMS) analysis. Sulfur demonstrated n-type behavior with an activation energy of 0.9 eV. Sodium was found to diffuse into diamond with an average diffusion coefficient of 7.2 � 10 � 14 cm 2 /s at 750 � C. The different sources of sulfur provided qualitative information about competing mechanisms in the diffusion process.
主要作者在这里报告了他1999年博士论文(Matthew Keith West，“硫在天然钻石中的扩散:辐射探测中的表征和应用”)中所做的主要工作。博士学位论文，美国密苏里大学哥伦比亚分校(1999)。在这项研究中，我们构建了一个光活化场增强扩散反应器(FEDOA)，测试并使用它将硫和钠扩散到抛光的天然金刚石片中。硫的各种化学来源被用于从气态、液态和固相扩散。从二次离子质谱(SIMS)分析确定的硫浓度曲线中，计算出温度为450-1050℃时，扩散系数范围为10 - 15 cm 2 /s至10 - 14 cm 2 /s。硫表现为n型行为，活化能为0.9 eV。在750℃时，钠扩散到金刚石中的平均扩散系数为7.2 ~ 10 ~ 14 cm 2 /s。不同来源的硫提供了扩散过程中竞争机制的定性信息。
{"title":"Sulfur and Sodium: Diffusion of Potential Donors into Natural Diamond","authors":"M. West, M. Prelas, R. Tompson, A. Khomich","doi":"10.1177/1524511X02043541","DOIUrl":"https://doi.org/10.1177/1524511X02043541","url":null,"abstract":"The principal author reports here the main elements of work performed as part of his 1999 Ph.D. dissertation (Matthew Keith West, ''Diffusion of Sulfur into Natural Diamond: Characterization and Applications in Radiation Detection''. Ph.D. Dissertation, University of Missouri-Columbia, USA (1999)). In this study a Field Enhanced Diffusion with Optical Activation (FEDOA) reactor was constructed, tested, and employed to diffuse sulfur and sodium into polished, natural diamond plates. Various chemical sources of sulfur were used for diffusion from the gaseous, liquid, and solid phases. Diffusion coefficients in the range of 10 � 15 cm 2 /s to 10 � 14 cm 2 /s for temperatures 450-1050 � C, have been calculated for sulfur from concentration profiles determined from secondary ion mass spectroscopy (SIMS) analysis. Sulfur demonstrated n-type behavior with an activation energy of 0.9 eV. Sodium was found to diffuse into diamond with an average diffusion coefficient of 7.2 � 10 � 14 cm 2 /s at 750 � C. The different sources of sulfur provided qualitative information about competing mechanisms in the diffusion process.","PeriodicalId":246239,"journal":{"name":"Journal of Wide Bandgap Materials","volume":"162 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124027893","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-10-01DOI: 10.1177/1524511X02043540
A. V. Bulyga, V. Shipilo, P. Gielisse
The features and advantages of multicomponent compound cathodes for vacuum electronic devices are discussed. The effects of recent experimental data on the effective work function of a composite cathode with cubic boron nitride as the principal phase, are presented. Methods to reduce the work function of new materials so as to develop high(er) efficiency cathodes, are proposed.
{"title":"Effective Work Function of Cathodes Consisting of Cubic Boron Nitride and Aluminum Nitride","authors":"A. V. Bulyga, V. Shipilo, P. Gielisse","doi":"10.1177/1524511X02043540","DOIUrl":"https://doi.org/10.1177/1524511X02043540","url":null,"abstract":"The features and advantages of multicomponent compound cathodes for vacuum electronic devices are discussed. The effects of recent experimental data on the effective work function of a composite cathode with cubic boron nitride as the principal phase, are presented. Methods to reduce the work function of new materials so as to develop high(er) efficiency cathodes, are proposed.","PeriodicalId":246239,"journal":{"name":"Journal of Wide Bandgap Materials","volume":"39 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124648492","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-10-01DOI: 10.1177/1524511X02028020
A. Spitsyn, R. Tompson, M. Prelas, T. Ghosh
This paper presents results of charge carriers removal from 4H-SiC wafers. A new chemical reactor has been tested for forced diffusion purification (reversed diffusion) of SiC films. Different types of conditions have been used to purify SiC samples. A 5 mW (630-680 nm) laser has been used to improve results. I-V characteristic curves have been measured to verify changes in electrical properties of the samples. SIMS has been used to analyze the concentrations of impurities in the SiC samples before and after treatment. It has been demonstrated that the field enhanced by optical activation diffusion method can remove impurities such as N and B form SiC films. As a result, the electrical properties of the SiC wafers have been significantly improved during treatment, especially in cases where a laser is emplaced.
{"title":"Charge Carriers Removal from 4H-SiC Using Field Enhanced by Optical Activation Diffusion Method","authors":"A. Spitsyn, R. Tompson, M. Prelas, T. Ghosh","doi":"10.1177/1524511X02028020","DOIUrl":"https://doi.org/10.1177/1524511X02028020","url":null,"abstract":"This paper presents results of charge carriers removal from 4H-SiC wafers. A new chemical reactor has been tested for forced diffusion purification (reversed diffusion) of SiC films. Different types of conditions have been used to purify SiC samples. A 5 mW (630-680 nm) laser has been used to improve results. I-V characteristic curves have been measured to verify changes in electrical properties of the samples. SIMS has been used to analyze the concentrations of impurities in the SiC samples before and after treatment. It has been demonstrated that the field enhanced by optical activation diffusion method can remove impurities such as N and B form SiC films. As a result, the electrical properties of the SiC wafers have been significantly improved during treatment, especially in cases where a laser is emplaced.","PeriodicalId":246239,"journal":{"name":"Journal of Wide Bandgap Materials","volume":"53 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121823592","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-10-01DOI: 10.1177/1524511X02043536
M. Prelas, T. Ghosh, S. Loyalka, R. Tompson
Field Enhanced Diffusion with Optical Activation (FEDOA), a method developed in the authors' laboratory for adding impurities to diamond, has demonstrated that many types of impurities can be incorporated into natural diamond plates and CVD diamond films. This work reports the incorporation of hydrogen in type IIa diamond plates and CVD diamond films. The results indicate that hydrogen is attracted to diamond. Hydrogen is incorporated into different polycrystalline diamond films at different rates. The grain size of the diamond film seems to play a role in the rate of hydrogen incorporation. The best results for hydrogen storage (21% by mass) were with films with submicrometer grain sizes.
{"title":"Hydrogen Storage in Diamond Films","authors":"M. Prelas, T. Ghosh, S. Loyalka, R. Tompson","doi":"10.1177/1524511X02043536","DOIUrl":"https://doi.org/10.1177/1524511X02043536","url":null,"abstract":"Field Enhanced Diffusion with Optical Activation (FEDOA), a method developed in the authors' laboratory for adding impurities to diamond, has demonstrated that many types of impurities can be incorporated into natural diamond plates and CVD diamond films. This work reports the incorporation of hydrogen in type IIa diamond plates and CVD diamond films. The results indicate that hydrogen is attracted to diamond. Hydrogen is incorporated into different polycrystalline diamond films at different rates. The grain size of the diamond film seems to play a role in the rate of hydrogen incorporation. The best results for hydrogen storage (21% by mass) were with films with submicrometer grain sizes.","PeriodicalId":246239,"journal":{"name":"Journal of Wide Bandgap Materials","volume":"51 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114306486","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-10-01DOI: 10.1177/1524511X02043542
A. Spitsyn, M. Prelas, T. Ghosh, R. Tompson
This paper presents results of impurity removal from 6H-SiC wafers. A new chemical reactor has been tested for Field Enhanced Diffusion by Optical Activation (FEDOA) purification (reversed diffusion) of SiC films. Different conditions have been used to purify SiC samples including temperature variation, electrical field variation, variations in electrical current and optical activation. A 5 mW (630-680 nm) laser was used for optical activation. It was observed that optical activation has a major effect on ion drift rates. It was also observed that the magnitude of the electrical current enhanced ion drift rates as well by a postulated current drag mechanism. I-V characteristic curves were obtained to verify changes in the electrical properties of the samples. SIMS was used to analyze the concentrations of impurities in the SiC samples before and after treatment. It has been demonstrated that the field enhanced diffusion by optical activation method can remove impurities such as N and B from SiC films. As a result, the electrical properties of the 6H-SiC wafers have been significantly improved during treatment especially in cases where a laser is emplaced.
{"title":"Impurity Removal from 6H-SiC Using Field Enhanced Diffusion by Optical Activation Method","authors":"A. Spitsyn, M. Prelas, T. Ghosh, R. Tompson","doi":"10.1177/1524511X02043542","DOIUrl":"https://doi.org/10.1177/1524511X02043542","url":null,"abstract":"This paper presents results of impurity removal from 6H-SiC wafers. A new chemical reactor has been tested for Field Enhanced Diffusion by Optical Activation (FEDOA) purification (reversed diffusion) of SiC films. Different conditions have been used to purify SiC samples including temperature variation, electrical field variation, variations in electrical current and optical activation. A 5 mW (630-680 nm) laser was used for optical activation. It was observed that optical activation has a major effect on ion drift rates. It was also observed that the magnitude of the electrical current enhanced ion drift rates as well by a postulated current drag mechanism. I-V characteristic curves were obtained to verify changes in the electrical properties of the samples. SIMS was used to analyze the concentrations of impurities in the SiC samples before and after treatment. It has been demonstrated that the field enhanced diffusion by optical activation method can remove impurities such as N and B from SiC films. As a result, the electrical properties of the 6H-SiC wafers have been significantly improved during treatment especially in cases where a laser is emplaced.","PeriodicalId":246239,"journal":{"name":"Journal of Wide Bandgap Materials","volume":"371 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115991234","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"The Effects of Pores of Template on the Field Emission Properties of Template-Synthesized Array of Carbon Nanotubes","authors":"Y. Zhu, W. L. Wang","doi":"10.1177/152451102028021","DOIUrl":"https://doi.org/10.1177/152451102028021","url":null,"abstract":"","PeriodicalId":246239,"journal":{"name":"Journal of Wide Bandgap Materials","volume":"51 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133251823","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-07-01DOI: 10.1177/1524511X02010001001
A. Shulzhenko, M. Bezhenar, S. Bozhko, N. Belyavina, V. Markiv
{"title":"cBN→hBN Phase Transformation During Sintering of cBN and Al Powders at High Pressures and Temperatures","authors":"A. Shulzhenko, M. Bezhenar, S. Bozhko, N. Belyavina, V. Markiv","doi":"10.1177/1524511X02010001001","DOIUrl":"https://doi.org/10.1177/1524511X02010001001","url":null,"abstract":"","PeriodicalId":246239,"journal":{"name":"Journal of Wide Bandgap Materials","volume":"68 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130511672","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-07-01DOI: 10.1177/1524511X02010001002
A. Suarez, M. Prelas, T. Ghosh, R. Tompson, S. Loyalka, W. Miller, D. Viswanath
{"title":"Diffusion of Boron into Polycrystalline Diamond Films Using the Electric Field Enhanced Diffusion (EFED) Technique","authors":"A. Suarez, M. Prelas, T. Ghosh, R. Tompson, S. Loyalka, W. Miller, D. Viswanath","doi":"10.1177/1524511X02010001002","DOIUrl":"https://doi.org/10.1177/1524511X02010001002","url":null,"abstract":"","PeriodicalId":246239,"journal":{"name":"Journal of Wide Bandgap Materials","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134643939","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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