Morphological Transition in Diamond Thin-Films Induced by Boron in a Microwave Plasma Deposition Process

Modulating Band Gap of Boron Doping in Amorphous Carbon Nano-Film

Amorphous carbon (a-C) films are attracting considerable attention to due their large optical band gap (E_opt) range of 1–4 eV. But the hopping conducting mechanism of boron doping a-C (a-C:B) is still mysterious. To exploring the intrinsic reasons behind the semiconductor properties of a-C:B, in this work, the boron doping a-C (a-C:B) nano-film was prepared, and the growth rate and E_opt changing were analyzed by controlling the different experimental conditions of magnetron sputtering. A rapid deposition rate of 10.55 nm/min was obtained. The E_opt is reduced from 3.19 eV to 2.78 eV by improving the substrate temperature and sputtering power. The proportion of sp²/sp³ increasing was uncovered with narrowing the E_opt. The shrinking E_opt can be attributed to the fact that boron atoms act as a fluxing agent to promote carbon atoms to form sp² hybridization at low energy. Furthermore, boron atoms can impede the formation of σ bonds in carbon atom sp³ hybridization by forming B–C bonds with high energy, and induce the sp³ hybridization transfer to sp² hybridization. This work is significant to further study of amorphous semiconductor films.

Computational Predictions and Microwave Plasma Synthesis of Superhard Boron-Carbon Materials

Superhard boron-carbon materials are of prime interest due to their non-oxidizing properties at high temperatures compared to diamond-based materials and their non-reactivity with ferrous metals under extreme conditions. In this work, evolutionary algorithms combined with density functional theory have been utilized to predict stable structures and properties for the boron-carbon system, including the elusive superhard BC₅ compound. We report on the microwave plasma chemical vapor deposition on a silicon substrate of a series of composite materials containing amorphous boron-doped graphitic carbon, boron-doped diamond, and a cubic hard-phase with a boron-content as high as 7.7 at%. The nanoindentation hardness of these composite materials can be tailored from 8 GPa to as high as 62 GPa depending on the growth conditions. These materials have been characterized by electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, X-ray diffraction, and nanoindentation hardness, and the experimental results are compared with theoretical predictions. Our studies show that a significant amount of boron up to 7.7 at% can be accommodated in the cubic phase of diamond and its phonon modes and mechanical properties can be accurately modeled by theory. This cubic hard-phase can be incorporated into amorphous boron-carbon matrices to yield superhard materials with tunable hardness values.

Open Abdomen Management and Candida Infections: A Very Likely Link

OBJECTIVE

Laparostomy can be applied in trauma, abdominal sepsis, intra-abdominal hypertension, or compartment syndrome. Systemic infections, especially if complicated by Candida, are associated with a high risk of mortality.

METHODS

This is a single-centre retrospective case series of 47 cases admitted to our Department, which required laparostomy procedure; we analyzed the type of surgery, temporary abdominal closure, duration of open abdomen, complications, SOFA score, mortality with Candida infections, and empirical or targeted antifungal therapy.

RESULTS

We found that patients with Candida infection were related with a statistically significant difference (p < 0.05) with a complication after OA closure, total complications, time elapsed after OA application, time spent on the first surgical OA application, type of temporary abdominal closure that is used, and duration of the open abdomen. The use of empirical and targeted antifungal therapy is related to the duration of open abdomen too.

CONCLUSIONS

Management of the OA is often burdened by sepsis or septic shock, especially when complicated by Candida infection. Candida score is a validated tool to identify patients who can be treated empirically, but every situation must be considered on an individual basis.