Boron carbide is characterized by a unique combination of properties that make it a material of choice for a wide range of engineering applications. Boron carbide is used in refractory applications due to its high melting point and thermal stability; it is used as abrasive powders and coatings due to its extreme abrasion resistance; it excels in ballistic performance due to its high hardness and low density; and it is commonly used in nuclear applications as neutron radiation absorbent. In addition, boron carbide is a high temperature semiconductor that can potentially be used for novel electronic applications. This paper provides a comprehensive review of the recent advances in understanding of structural and chemical variations in boron carbide and their influence on electronic, optical, vibrational, mechanical, and ballistic properties. Structural instability of boron carbide under high stresses associated with external loading and the nature of the resulting disordered phase are also discussed.

Boron Carbide: Structure, Properties, and Stability under Stress

We report on the current properties of Al1-x InxN (x approximate to 0.18) layers lattice- matched ( LM) to GaN and their specific use to realize nearly strain- free structures for photonic and electronic applications. Following a literature survey of the general properties of AlInN layers, structural and optical properties of thin state- of- the- art AlInN layers LM to GaN are described showing that despite improved structural properties these layers are still characterized by a typical background donor concentration of ( 1 - 5) x 10(18) cm(-3) and a large Stokes shift (similar to 800 meV) between luminescence and absorption edge. The use of these AlInN layers LM to GaN is then exemplified through the properties of GaN/ AlInN multiple quantum wells ( QWs) suitable for near- infrared intersubband applications. A built- in electric field of 3.64MVcm(-1) solely due to spontaneous polarization is deduced from photoluminescence measurements carried out on strain- free single QW heterostructures, a value in good agreement with that deduced from theoretical calculation. Other potentialities regarding optoelectronics are demonstrated through the successful realization of crack- free highly reflective AlInN/ GaN distributed Bragg reflectors ( R > 99%) and high quality factor microcavities ( Q > 2800) likely to be of high interest for short wavelength vertical light emitting devices and fundamental studies on the strong coupling regime between excitons and cavity photons. In this respect, room temperature ( RT) lasing of a LM AlInN/ GaN vertical cavity surface emitting laser under optical pumping is reported. A description of the selective lateral oxidation of AlInN layers for current confinement in nitride- based light emitting devices and the selective chemical etching of oxidized AlInN layers is also given. Finally, the characterization of LM AlInN/ GaN heterojunctions will reveal the potential of such a system for the fabrication of high electron mobility transistors through the report of a high two- dimensional electron gas sheet carrier density ( n(s) similar to 2.6 x 10(13) cm(-2)) combined with a RT mobility mu(e) similar to 1170 cm(2) V-1 s(-1) and a low sheet resistance, R similar to 210 Omega square.

https://iopscience.iop.org/article/10.1088/0022-3727/40/20/S16/pdf

Current status of AlInN layers lattice-matched to GaN for photonics and electronics

A wide range of biomedical devices is applied clinically in contact with blood. Tailoring the surface properties of the involved biomaterials is a common approach to enhance performance and to limit adverse reactions. This review summarizes current trends in coating technologies developed for that purpose. Inorganic coatings were shown to substantially improve the durability and inertness of biomaterials while a number of advanced polymer coatings were demonstrated to be very effective by targeting specific biochemical pathways. However, to fully utilize the power of these bioactive coatings safety issues need to be thoroughly addressed in future studies.

Current strategies towards hemocompatible coatings

We report on a novel MoS2/S-doped g-C3N4 heterojunction film with high visible-light photoelectrochemical (PEC) performance. The heterojunction films are prepared by CVD growth of S-doped g-C3N4 film on indium–tin oxide (ITO) glass substrates, with subsequent deposition of a low bandgap, 1.69 eV, visible-light response MoS2 layer by hydrothermal synthesis. Adding thiourea into melamine as the coprecursor not only facilitates the growth of g-C3N4 films but also introduces S dopants into the films, which significantly improves the PEC performance. The fabricated MoS2/S-doped g-C3N4 heterojunction film offers an enhanced anodic photocurrent of as high as ∼1.2 × 10–4 A/cm2 at an applied potential of +0.5 V vs Ag/AgCl under the visible light irradiation. The enhanced PEC performance of MoS2/S-doped g-C3N4 film is believed due to the improved light absorption and the efficient charge separation of the photogenerated charge at the MoS2/S-doped g-C3N4 interface. The convenient preparation of carbon nitride based ...

Fabrication and Enhanced Photoelectrochemical Performance of MoS2/S-Doped g-C3N4 Heterojunction Film

The electronic, mechanical properties and theoretical hardness of chromium carbides by first-principles calculations

http://liu.diva-portal.org/smash/get/diva2:23231/FULLTEXT01

Phase control of Al2O3 thin films grown at low temperatures

The atomic arrangement in $s{p}^{2}$-dominated carbon (C) and carbon nitride $({\mathrm{CN}}_{x})$ thin films has been studied by Raman spectroscopy as a function of substrate temperature and, in the case of ${\mathrm{CN}}_{x}$, different N incorporation routes (growth methods) In this way, materials composing graphitelike, fullerenelike (FL), and paracyanogenlike structures have been compared The results show that each type of arrangement results in a characteristic set of the Raman spectra parameters, which describe the degree of aromatic clustering, bond length, and angle distortion and order in sixfold structures In the case of C films, the atomic structure evolves with substrate temperature from a disordered network to nanocrystalline planar graphitic configurations, with a progressive promotion in size and ordering of sixfold ring clusters Nitrogen incorporation favors the promotion of sixfold rings in highly disordered networks produced at low temperatures, but precludes the formation of extended graphiticlike clusters at elevated substrate temperatures $(g700\phantom{\rule{03em}{0ex}}\mathrm{K})$ In the latter case, N introduces a high degree of disorder in sixfold ring clusters and enhances the formation of a FL microstructure The formation and growth of aromatic clusters are discussed in terms of substrate temperature, N incorporation, growth rate, film-forming sources, and concurrent bombardment by hyperthermal particles during growth

Sixfold ring clustering insp2-dominated carbon and carbon nitride thin films: A Raman spectroscopy study

Growth regimes and metal enhanced 6-fold ring clustering of carbon in carbon-nickel composite thin films

Electronic structure and mechanical properties of Cr7C3

The effect of energy supplied to the growing alumina film on the composition and structure has been investigated by varying substrate temperature and substrate bias potential. The constitution and ...

U. Kreissig

Papers

Phase control of Al2O3 thin films grown at low temperatures

Sixfold ring clustering insp2-dominated carbon and carbon nitride thin films: A Raman spectroscopy study

Growth regimes and metal enhanced 6-fold ring clustering of carbon in carbon-nickel composite thin films

Electronic structure and mechanical properties of Cr7C3

Effect of Ion Energy on Structure and Composition of Cathodic Arc Deposited Alumina Thin Films