N.R. Parikh

Single‐crystal diamond plate liftoff achieved by ion implantation and subsequent annealing

We describe a new method for removing thin, large area sheets of diamond from bulk or homoepitaxial diamond crystals. This method consists of an ion implantation step, followed by a selective etching procedure. High energy (4–5 MeV) implantation of carbon or oxygen ions creates a well‐defined layer of damaged diamond that is buried at a controlled depth below the surface. For C implantations, this layer is graphitized by annealing in vacuum, and then etched in either an acid solution, or by heating at 550–600 °C in oxygen. This process successfully lifts off the diamond plate above the graphite layer. For O implantations of a suitable dose (3×1017 cm−2 or greater), the liftoff is achieved by annealing in vacuum or flowing oxygen. In this case, the O required for etching of the graphitic layer is also supplied internally by the implantation. This liftoff method, combined with well‐established homoepitaxial growth processes, has considerable potential for the fabrication of large area single crystalline dia...

Deposition of copper oxide thin films on different substrates by pulsed excimer laser ablation

Stoichiometric films of cupric and cuprous oxide are deposited on Si, MgO, and Y‐ZrO2 substrates by pulsed excimer laser ablation technique. It is found that the equilibrium phase diagram based considerations dictate the phase formation. The films are characterized by small‐angle x‐ray diffraction, infrared, and UV‐visible spectroscopies and Rutherford backscattering spectroscopy. It is shown that epitaxy of Cu2O films can be realized on single crystal MgO (100) substrates and the corresponding film resistivity is of the order of 40–60 Ω cm.

Heteroepitaxial structures of SrTiO3/TiN on Si(100) by in situ pulsed laser deposition

High‐quality ceramics based heteroepitaxial structures of oxide‐nitride‐semiconductors, i.e., SrTiO3/TiN/Si(100) have been fabricated by in situ pulsed laser deposition. The dependence of substrate temperature and oxygen partial pressure on the crystalline quality of the SrTiO3 films on Si with epitaxial TiN template has been examined. We found that epitaxial growth occurs on TiN/Si(100) above 500 °C, initially at a reduced O2 pressure (10−6 Torr), and followed by a deposition in the range of 5–10×10−4 Torr. X‐ray diffraction (Θ, ω, and Φ scans) and transmission electron microscope (TEM) results revealed an excellent alignment of SrTiO3 and TiN films on Si(100) with a cube‐on‐cube epitaxy. Rutherford backscattering and ion channeling results show a channeling minimum yield (χmin) of ∼13% for the SrTiO3 films. High‐resolution TEM results on the SrTiO3/TiN interface show that the epitaxial SrTiO3 film is separated from the TiN by an uniform 80–90 A crystalline interposing layer presumably of TiNxO1−x (oxy‐n...

Metalorganic chemical vapor deposition and characterization of the In‐As‐Sb‐Bi material system for infrared detection

We report the first results pertaining to the growth by metalorganic chemical vapor deposition of InSb1−xBix (0.01<x<0.14) and InAs1−x−ySbyBix with 0.5<y<0.7 and 0.01<x<0.04 epitaxial films on both semi‐insulating GaAs(100) and InSb(100) substrates. Electrical measurements for the undoped InSb0.99Bi0.01 epitaxial layers show a room‐temperature mobility of 20 215 cm2/V s with a carrier concentration of ND−NA ∼1016 cm−3. A degradation in the surface morphology of the InSb1−xBix and InAsSbBi epitaxial films correspond to an increase in the InBi mole fraction was observed. We attribute this deterioration in surface morphology to the formation of polycrystalline phases of Bi and the growth of metallic bismuth‐antimony crystallites.

Ion implantation of epitaxial GaN films: damage, doping and activation

Single-crystal GaN films grown on AlN buffer layers previously deposited on 6H-SiC(0001) were studied for radiation damage and its recovery using Rutherford backscattering/channeling, photoluminescence, and cross-sectional TEM. The highest fluence of (1e15 cm{sup -2}) 110 keV Mg and 160 keV Si produced little damage at implantation temperature 550 C. RT damage was higher for same fluences compared to 550 C implantation. The damage was partially annealed by RTA at 1000 C, however, this was not enough to recover the PL signal even for the lowest fluence (1e14 cm{sup -2}). XTEM of as-implanted samples revealed small clusters of defects extended beyond the projected ion range. To recover damage completely, perhaps one needs to go either much higher RTA temperature and/or implant samples in a smaller fluence increment and anneal in between implants to recover the damage.

Conducting oxide electrodes for ferroelectric films

Abstract Suitability of oxide electronic conductors [e.g. ruthenium oxide (RuOx) and indium-tin-oxide (ITO)] as contact metallization for ferroelectric films (e.g. PbZrxTi1−xO3) was investigated using techniques such as Rutherford backscattering spectrometry, x-ray diffraction and electron spectroscopy for chemical analysis. Thin films of RuOx and ITO were deposited on Si substrates by reactive sputtering. Either PbO or PZT (x = 0.53) films were deposited onto the conducting oxides and the specimens were annealed at various temperatures between 400°C and 700°C. Less intermixing was found in Si/RuOx/ PZT films when compared to Si/ITO/PZT under similar processing conditions. The ferroelectric properties of PZT films on RuOx electrodes are compared to those on Pt electrodes. The PZT films show improved fatigue properties on RuOx electrodes.

Regrowth of radiation-damaged layers in natural diamond

Abstract The regrowth of radiation-damaged layers created by carbon ion implantation in natural diamond was investigated by the Rutherford backscattering/channeling technique and by optical absorption. We present the first results of rapid thermal annealing of the implanted samples directly from the 77 K implantation temperature to 1100° C as well as data for isochronal annealing. We found that isochronal annealing up to 900° C was more effective than rapid thermal annealing for amorphized samples. The critical dose for amorphization of diamond was between 1.65 × 1015 and 3 × 1015 cm−2 for 200 keV carbon ion implantation at 77 K.

Transition between Ge segregation and trapping during high‐pressure oxidation of GexSi1−x/Si

A transition from Ge segregation to trapping during high‐pressure oxidation of GexSi1−x alloys has been observed. The atomic fraction x of Ge was varied from 0.4% to 26%, and oxidations were performed at 740 °C under 102 atm of dry O2. It was observed that the effect of oxidation on the Ge distribution could be divided into three stages. In the initial stage of the oxidation, Ge was segregated from the growing oxide and accumulated in a Ge‐rich layer at the oxide/alloy interface. For alloys with high Ge content this initial stage was very short. In the second stage of oxidation, after a critical quantity of Ge had accumulated at the interface, there was a transition from segregation to trapping of Ge in the oxide. In the third stage, the critical amount of Ge remained segregated at the interface, and the final oxide layer was Ge free. A kinetic model based on a steady‐state equilibrium between the diffusive flux of Si across the Ge‐rich layer and the rate of Si consumption by the oxidation reaction predic...

Ultra Shallow Junction Formation Using Diffusion from Silicides II . Diffusion in Silicides and Evaporation

The phenomena associated with dopant redistribution in TiSi 2 , CoSi 2 , NiSi, Pd 2 Si, and PtSi, as would be used in a silicide-As-diffusion-source process, were examined. Segregation of dopant (B) into a surface layer, evaporation of dopant, and slow, grain-boundary diffusion, were found to occur in annealed, implanted silicides. For CoSi 2 , 1.6×10 14 boron atoms/cm, were found to segregate to the silicide surface, independent of the initial implant dose, possibly as B 2 O 3

Observation of antiphase domain boundaries in GaAs on silicon by transmission electron microscopy

Boundaries between different antiphase domains have been unambiguously identified in heteroepitaxial GaAs on silicon substrates by transmission electron microscopy. A simple and reliable method is described for assessing the presence or absence of these domain boundaries in GaAs. The domain size was found to be as small as ∼0.1 μm in GaAs that had been grown on nominal Si(001) in which a buried, implanted oxide had been previously formed. These boundaries are expected to degrade electrical performance and device reliability modify electronic transport and degrade device performance.