Dissociation mechanism for solid-phase epitaxy of silicon in the Si <100>/Pd2Si/Si (amorphous) system

Solid-phase epitaxial growth (SPEG) of silicon was investigated by a tracer technique using radioactive 31Si formed by neutron activation in a nuclear reactor. After depositing Pd and Si onto activated single-crystal silicon substrates, Pd2Si was formed with about equal amounts of radioactive and nonradioactive Si during heating at 400 °C for 5 min. After an 1-sec annealing stage (450-->500 °C in 1 h) this silicide layer, which moves to the top of the sample during SPEG, is etched off with aqua regia. From the absence of radioactive 31Si in the etch, it is concluded that SPEG takes place by a dissociation mechanism rather than by diffusion

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Heterostructure by solid‐phase epitaxy in the Si〈111〉/Pd/Si (amorphous) system

When a thin film of Pd reacts with a 〈111〉 Si substrate, a layer of epitaxial Pd_2Si is formed. It is shown that Si can grow epitaxially on such a layer by solid‐phase reaction

Depth dependence of atomic mixing by ion beams

Ion backscattering spectrometry has been used to investigate the depth dependence of atomic mixing induced by ion beams. Samples consisting of a thin Pt (or Si) marker a few tens of angstroms thick buried at different depths in a deposited Si (or Pt) layer were bombarded with Xe+ of 300 keV at 2×10^16 cm^–2 dose and Ar+ of 150 keV at 5×10^15cm^–2 dose. Significant spreading of the marker was observed as a result of ion irradiation. The amount of spreading was measured as a function of depth of the marker, which was then compared with the deposited energy distribution. Measurements of this kind promise new insight into the nature of the interaction between ion beams and solids

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 µm thick), a very thin intermediate layer of Sb (nominally 5 Å), and a thin lower layer of Pd (~500 Å), all electron-gun deposited on top of a single-crystal substrate (1–10 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

Growth mechanism for solid-phase epitaxy of Si in the Si <100>/Pd2Si/Si(amorphous) system studied by a radioactive tracer technique

A tracer technique using radioactive 31Si (T1/2=2.62 h) was used to study solid-phase epitaxial growth (SPEG) of silicon. After depositing Pd and Si onto single-crystal substrates which had been activated in a nuclear reactor, Pd2Si was formed with about equal amounts of radioactive and nonradioactive silicon during heating at 400 °C for 5 min. After a second annealing stage (450 °C-->500 °C in 1 h) the silicide layer which moves to the top of the sample during SPEG was etched off with aqua regia. From the absence of radioactive 31Si in the etchant solution it is concluded that SPEG takes place by dissociation of the Pd2Si layer at the single-crystal interface to provide free Si for epitaxial growth, while new silicide is formed at the interface with the amorphous Si. These results were confirmed by evaporating radioactive silicon onto nonactivated silicon substrates before evaporation of Pd and stable amorphous Si and by measuring the activity in the SPEG sample before and after etching off the silicide layer

Cutaneous metastases from cholangiocarcinoma following percutaneous transhepatic biliary drainage: Case report and literature review

AbstractPercutaneous transhepatic biliary drainage (PTBD) is commonly used in the management of cholangiocarcioma. Major and minor complications of PTBD such as cholangitis, haemorrhage and catheter dislocation are well documented. A lesser reported complication are cutaneous metastases following PTBD for cholangiocarcinoma.We report a case of a 79 year old man who presented with right upper quadrant pain, jaundice and weight loss, with dilated intra-hepatic bile ducts on imaging. The cytology results from a sample taken during endoscopic retrograde cholangiopancreatography were highly suspicious of cholangiocarcioma. A PTBD was subsequently performed and bilateral metal biliary stents were placed without external drainage. Five months after the PTBD he was found to have a hard nodule under the PTBD puncture site. The nodule was excised and the histology confirmed a cholangiocarcinoma metastasis.A review of the literature identified twelve cases of cutaneous metastases from cholangiocarcinoma, following PTBD. In addition, tumour seeding along the catheter tract following PTBD, with metastatic deposits on the abdominal wall, peritoneoum, chest wall, pleural space, and liver parenchyma have also been reported.Health care professionals should be aware of this rare complication and offer appropriate management options to patients

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 1988–2008 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