Publication IV
نویسندگان
چکیده
We have applied positron annihilation spectroscopy to study in-grown vacancy defects in bulk aluminium nitride (AlN) crystals grown by physical vapor transport. We interpret the lowest lifetime value of about 155ps, measured at low temperatures, to represent the annihilations from the free state of the positron in the crystal lattice. The increased lifetime at high temperatures is an indication of positrons annihilating as trapped at vacancy defects, and a second lifetime component could be separated from the lifetime spectra at temperatures above 400K. The same lifetime component t2 1⁄4 210710ps was found in all AlN samples. This component can be attributed to positrons annihilating at Al vacancies, possibly complexed with impurities such as oxygen, present at concentrations in the 10 cm 3 range in the samples. In addition to Al vacancies, negatively charged non-open volume defects acting as shallow hydrogenic traps for positrons were detected, with concentrations of about 10 cm 3 or higher. These defects are the dominant negative acceptor defects
منابع مشابه
طبقه بندی، همه گیر شناسی و هم ابتلایی اختلالات اعتیاد 1
Revised only twice in the 28 – year period from 1952 to 1980, the American Psychiatric Association`s Diagnostic and Statistical Manual of Mental Disorders (DSM) has been amended two more times in half as many years, with the publication of DSM – III – R in 1987 and of DSM – IV in 1994. The DSM counterpart in use outside of North America, the International Classification of Diseases (ICD), also ...
متن کاملPublication Ethics: A Case Series with Recommendations According to Committee on Publication Ethics (COPE)
Ethical misconduct is not a new issue in the history of science and literature. However, ethical misconducts in science have grown considerably in the modern era which is due to emphasis on the scientific proliferation in research institutes and gauging scientists according to their publications. In the current case series, several misconducts occurring over the previous years in Mashhad Univer...
متن کاملPublication Ethics: Many Facets, Collaboration Required
Sir, the recent publication on “Publication Ethics” is very interesting (1). The article by Fazly Bazzaz and Sadeghi demonstrated many interesting cases of misconducts. Indeed, the misconducts can be seen in many ways. As mentioned in the present publication, both author and editor can perform publication misconducts. Nevertheless, the problem has many more facets. Sometimes,...
متن کاملتأخیر در انتشار مجلههای علمی: مطالعه نشریات مصوب وزارت علوم، تحقیقات و فناوری ایران
: Publication delay is a negative phenomenon in scientific information dissemination. The current research studies the publication delay of scientific journals accredited by the Ministry of Science, Research & Technology of Iran. It also investigates the association between journals’ characteristics and their publication lag. This study employs the applied research method. All 1156 journals of ...
متن کامل