1,205 research outputs found
Influence of atomic mixing and preferential sputtering on depth profiles and interfaces
Atomic mixing and preferential sputtering impose a depth resolution limit on the use of sputter sectioning to measure the composition of metalâsemiconductor interfaces. Experimental evidence obtained with the PtâSi system is used to demonstrate ionâinduced atomic mixing and then its effect on sputter etching and depth profiling. Starting with discrete layer structures, a relatively low ion dose (âł3Ă10^(15) cm^(â2)) first produced a mixed surface layer with thickness comparable to the ion range. Higher ion doses then result in successive sputter etching and continual atomic mixing over a constant surface layer thickness. A model is developed that is based on a sputter removal (including preferential sputtering) of atoms at the surface and a uniform mixing of atoms over a constant thickness. The model predicts the influences of atomic mixing and preferential sputtering on the depth profiling of thinâfilm structures and interfaces
Heterostructure by solidâphase epitaxy in the Siă111ă/Pd/Si (amorphous) system
When a thin film of Pd reacts with a ă111ă Si substrate, a layer of epitaxial Pd_2Si is formed. It is shown that Si can grow epitaxially on such a layer by solidâphase reaction
Antimony doping of Si layers grown by solid-phase epitaxy
We report here that layers of Si formed by solid-phase epitaxial growth (SPEG) can be doped intentionally. The sample consists initially of an upper layer of amorphous Si (~1 ”m thick), a very thin intermediate layer of Sb (nominally 5 Ă
), and a thin lower layer of Pd (~500 Ă
), all electron-gun deposited on top of a single-crystal substrate (1â10 Ω cm, p type, orientation). After a heating cycle which induces epitaxial growth, electrically active Sb atoms are incorporated into the SPEG layer, as shown by the following facts: (a) the SPEG layer forms a p-n junction against the p-type substrate, (b) the Hall effect indicates strong n-type conduction of the layer, and (c) Auger electron spectra reveal the presence of Sb in the layer
Calibration and Irradiation Study of the BGO Background Monitor for the BEAST II Experiment
Beam commissioning of the SuperKEKB collider began in 2016. The Beam Exorcism
for A STable experiment II (BEAST II) project is particularly designed to
measure the beam backgrounds around the interaction point of the SuperKEKB
collider for the Belle II experiment. We develop a system using bismuth
germanium oxide (BGO) crystals with optical fibers connecting to a multianode
photomultiplier tube (MAPMT) and a field-programmable gate array (FPGA)
embedded readout board for monitoring the real-time beam backgrounds in BEAST
II. The overall radiation sensitivity of this system is estimated to be
Gy/ADU (analog-to-digital unit) with the standard
10 m fibers for transmission and the MAPMT operating at 700 V. Our -ray
irradiation study of the BGO system shows that the exposure of BGO crystals to
Co -ray doses of 1 krad has led to immediate light output
reductions of 25--40%, and the light outputs further drop by 30--45% after the
crystals receive doses of 2--4 krad. Our findings agree with those of the
previous studies on the radiation hard (RH) BGO crystals grown by the low
thermal gradient Czochralski (LTG Cz) technology. The absolute dose from the
BGO system is also consistent with the simulation, and is estimated to be about
1.18 times the equivalent dose. These results prove that the BGO system is able
to monitor the background dose rate in real time under extreme high radiation
conditions. This study concludes that the BGO system is reliable for the beam
background study in BEAST II
Efficacy of HIV/STI behavioral interventions for heterosexual African American men in the United States: a meta-analysis
This meta-analysis estimates the overall efficacy of HIV prevention interventions to reduce HIV sexual risk behaviors and sexually transmitted infections (STIs) among heterosexual African American men. A comprehensive search of the literature published during 1988â2008 yielded 44 relevant studies. Interventions significantly reduced HIV sexual risk behaviors and STIs. The stratified analysis for HIV sexual risk behaviors indicated that interventions were efficacious for studies specifically targeting African American men and men with incarceration history. In addition, interventions that had provision/referral of medical services, male facilitators, shorter follow-up periods, or emphasized the importance of protecting family and significant others were associated with reductions in HIV sexual risk behaviors. Meta-regression analyses indicated that the most robust intervention component is the provision/referral of medical services. Findings indicate that HIV interventions for heterosexual African American men might be more efficacious if they incorporated a range of health care services rather than HIV/STI-related services alone
Limits of composition achievable by ion implantation
In highâdose ion implantation for materials modification, the maximum concentration of the implanted species is determined by ionâinduced erosion (sputtering) of the implanted layer. In this review, we consider the influence of preferential sputtering and atomic mixing. The maximum concentration of the implanted species is given roughly by r/S and extends over a depth W where S is the sputtering yield, r is the preferential sputtering factor (1/2âČrâČ2) and W is a depth comparable to the ion range. Good agreement between calculation and experiment is found for 150âkeV Au implanted into Cu or Fe. Surface conditions, such as oxide layers or carbon films, can alter sputtering yields and can lead to the mixing of surface contaminants throughout the implanted layer. Implantation of species A into a target material AB results in a different concentration limit, but again preferential sputtering and the total sputtering yield set this limit. Calculations for PtSi indicate that the concentration of Si is decreased by implantation of Si for Sâł3
Utility of Parental Mediation Model on Youthâs Problematic Online Gaming
The Parental Mediation Model PMM) was initially designed to regulate childrenâs attitudes towards the traditional media. In the present era, because of prevalent online media there is a need for similar regulative measures. Spending long hours on social media and playing online games increase the risks of exposure to the negative outcomes of online gaming. This paper initially applied the PMM developed by European Kids Online to (i) test the reliability and validity of this model and (ii) identify the effectiveness of this model in controlling problematic online gaming (POG). The data were collected from 592 participants comprising 296 parents and 296 students of four foreign universities, aged 16 to 22 years in Kuala Lumpur (Malaysia). The study found that the modified model of the five-factor PMM (Technical mediation, Monitoring mediation, Restrictive mediation, Active Mediation of Internet Safety, and Active mediation of Internet Use) functions as a predictor for mitigating POG. The findings suggest the existence of a positive relation between âmonitoringâ and ârestrictiveâ mediation strategies and exposure to POG while Active Mediation of Internet Safety and Active mediation of Internet use were insignificant predictors. Results showed a higher utility of âtechnicalâ strategies by the parents led to less POG. The findings of this study do not support the literature suggesting active mediation is more effective for reducing youthâs risky behaviour. Instead, parents need to apply more technical mediations with their children and adolescentsâ Internet use to minimize the negative effects of online gaming
Expression of Extracellular Matrix Proteins in Human Periodontal Ligament Cells During Mineralization In Vitro
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142249/1/jper0320.pd
- âŠ