Doping Diamond for Electronic Applications

Diamond exhibits extraordinary physical and chemical properties, many of which have already found application in tribology, thermal management, and optics. Furthermore, diamond is also a wide-band-gap semiconductor which, when doped, can lead to the realization of electronic and optoelectronic devices with exceptional properties. Diamond can now be doped p-type, with boron, both during chemical vapor deposition (CVD) diamond film growth and by ion-implantation, and n-type, with phosphorus, during CVD growth. This paper reviews the current status of diamond doping and describes the electronic properties of the doped layers. Some potential applications of doped semiconducting diamond are described.     

Processing of photonic crystal nanocavity for quantum information in diamond

The realization of photonic crystals (PC) in diamond is of major importance for the entire field of spintronics based on fluorescent centers in diamond. The processing steps for the case of diamond differ from those commonly used, due to the extreme chemical and mechanical properties of this material. The present work summarizes the state of the art in the realization of PC's in diamond. It is based on the creation of a free standing diamond membrane into which the desired nano-sized patterns are milled by the use of Focused-Ion-Beam (FIB). The optimal fabrication-oriented structure parameters are predicted by simulations. The milling strategies, the method of formation the diamond membrane, recipes for dielectric material-manipulation in FIB and optical characterization constraints are discussed in conjunction with their implication on PC cavity design. The thus produced structures are characterized via confocal photoluminescence.     

Cardiac manifestations of ochronosis

A 68-year-old woman with ochronosis was admitted with congestive heart failure. A typical ejection murmur of aortic stenosis was ausculated and was documented on a phonocardiogram. The patient subsequently died, and at autopsy extensive deposition of ochronotic pigment was found on the aortic valve. This valve had no other anatomic abnormalities. Thus ochronosis should be considered in the differential diagnosis of aortic stenosis.     

The strength,fracture toughness,and low cycle fatigue behavior of 17-4 PH stainless steel

The influence of microstructure on the strength, fracture toughness and low cycle fatigue behavior of 17-4 PH stainless steel has been examined. Aging hardening involves initial formation of coherent copper-rich clusters which transform to incoherent fee ∈-copper precipitates upon further aging. The changes in strength level and strain hardening rates observed during aging are consistent with previously suggested models for precipitation hardening based on differing elastic moduli. The fracture toughness and fatigue crack growth rates were shown to be a function of microstructure and environment. At equivalent strength levels overaging resulted in a higher fracture toughness than did underaging. The fatigue crack growth rates increased with increasing strength level and humidity but were not a function of toughness level. Attempts to correlate the fatigue crack growth rates with monotonie tensile properties were unsuccessful. However when final failure obeyed a critical strain criteria, the fracture toughness behavior could be reasonably described and related to preferential void nucleation and growth at δ-ferrite-matrix interfaces.     

The structure and properties of thermomechanically treated β-III titanium

Beta-III titanium (Ti-11.5Mo-5.5Zr-4.5Sn) was solutionized above the β-transus, water-quenched and deformed by rolling at room temperature. The deformation accelerated the aging kinetics at all temperatures up to the β transus. The thermomechanically treated (TMT) alloy always had higher strength than the conventionally heat treated (CHT) alloy; the effect being most marked when the aging product was normally α in a β matrix. In addition, the ductility and notched impact resistance of TMT β-III was greater than that of the CHT alloy in the over-aged condition. The TMT did not alter the morphology of the ellipsoidal α phase formed at low aging temperatures and short aging times, respectively. Here the strengthening increase is attributed to strain hardening of the initial β + ω microstructure. The deformation did substantially change the morphology of the Widmanstätten α phase that formed at higher aging temperatures. In particular, the Widmanstätten α plates were much finer and the β grain boundaries were no longer a preferred precipitation site following TMT. At the highest aging temperatures, the TMT material developed a cell structure of about 1 μ in diameter.     

Shallow donors with high n-type electrical conductivity in homoepitaxial deuterated boron-doped diamond layers

Diamond is a unique semiconductor for the fabrication of electronic and opto-electronic devices because of its exceptional physical and chemical properties. However, a serious obstacle to the realization of diamond-based devices is the lack of n-type diamond with satisfactory electrical properties. Here we show that high-conductivity n-type diamond can be achieved by deuteration of particularly selected homo-epitaxially grown (100) boron-doped diamond layers. Deuterium diffusion through the entire boron-doped layer leads to the passivation of the boron acceptors and to the conversion from highly p-type to n-type conductivity due to the formation of shallow donors with ionization energy of 0.23 eV. Electrical conductivities as high as 2omega(-1) x cm(-1) with electron mobilities of the order of a few hundred cm2 x V(-1) x s(-1) are measured at 300 K for samples with electron concentrations of several 10(16) x cm(-3). The formation and break-up of deuterium-related complexes, due to some excess deuterium in the deuterated layer, seem to be responsible for the reversible p- to n-type conversion. To the best of our knowledge, this is the first time such an effect has been observed in an elemental semiconductor.     

On the distribution of carbon in martensite

The statistical-mechanics of a generalized perfect lattice gas is used to describe the distribution of interstitial solute atoms in martensite. In untempered martensite, partitioning of mobile interstitial carbon occurs between normal octahedral interstitial sites and those distorted sites around immobile dislocations. The statistics adopted acknowledge the finite number of each kind of site per unit volume of martensite. The dislocation density, fraction of twinned martensite, and the arrangement of dislocations are all input variables in the calculations. The principal quantities calculated are the fraction of carbon atoms segregated to dislocations and the fraction of distorted sites occupied as functions of the carbon content and substructure. The equilibrium distribution of carbon is also determined for tempering conditions where either ∈-carbide or cementite may precipitate. Here, the change in the solubility limit of ferrite with dislocation density is predicted. In untempered low carbon martensites (at 300°K) 85 pct of the carbon will be segregated to dislocations at equilibrium. This value decreases to 60 pct in an 0.80 wt pct C steel. Less than 5 pct of the distorted sites are filled when the dislocation distribution is uniform. Much higher concentrations occur when the long range stresses of the dislocations are relaxed and the mean carbon/dislocation interaction energy increases. Analogous results are presented for the equilibrium among carbides, normal sites, and distorted sites. The predictions of the lattice gas model are in agreement with numerous independent experimental observations. David Kalish, formerly withLockheed-Georgia Co. E. M. Roberts, formerly with Lockheed-Georgia Co.     

Organizational creativity‐innovation process and breakthrough under time constraints: Mid‐point transformation

Time, as a constraining resource, is an important factor in organizational creativity processes. Yet we know little about its role in influencing the creative‐innovative process. This paper uses a case study to integrate three process‐oriented theories concerning the importance of process mid‐points and breakthrough as time resources dissipate. The context we examine is the design process of an exhibition of industrial innovations at the Science Museum in Jerusalem. We argue that actors select a course of action at approximately the temporal mid‐point of a process and that this course of action is itself creative and leads to a breakthrough transformation. Two types of mid‐point creative breakthrough transformation are classified as recombining and pruning. We suggest a theoretical integration and further directions for research.     

Reversible Switch Memory Effect in Hydrogen‐Terminated Ultrananocrystalline Diamond

Innovative memory switch devices require reliable bistable conductance properties. It would be desirable if such bistable characteristics were available in robust solid state materials, such as diamond, which benefit from outstanding physical properties. A bistable current with reversible switching effect from surface transfer doped ultrananocrystalline diamond thin films measured by electron field emission is reported. This switching is manifested by the appearance of huge jumps in the current emission, up to four orders of magnitude, that occur at specific extracting electric field values. Persistent hysteresis is exhibited whenever the field is ramped down. It is proposed that these phenomena are the result of resonant‐tunneling through a double barrier junction composed of tetrahedral amorphous carbon (ta‐C)/nanodiamond/adsorbent/vacuum. This finding may pave the way for the realization of novel types of memory switch devices with unprecedented performance.