V. Krishnamoorthy

University of Florida, Gainesville, Florida, United States

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Publications (39)59.21 Total impact

  • V. Krishnamoorthy · D. Venables · K. Moeller · K. S. Jones · B. Freer
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    ABSTRACT: (001) CZ silicon wafers were implanted with arsenic (As+) at energies of 10–50keV to doses of 2×1014 to 5×1015/cm2. All implants were amorphizing in nature. The samples were annealed at 700°C for 16hrs. The resultant defect microstructures were analyzed by XTEM and PTEM and the As profiles were analyzed by SIMS. The As profiles showed significantly enhanced diffusion in all of the annealed specimens. The diffusion enhancement was both energy and dose dependent. The lowest dose implant/annealed samples did not show As clustering which translated to a lack of defects at the projected range. At higher doses, however, projected range defects were clearly observed, presumably due to interstitials generated during As clustering. The extent of enhancement in diffusion and its relation to the defect microstructure is explained by a combination of factors including surface recombination of point defects, As precipitation, As clustering and end of range damage.
    No preview · Article · Jan 2012 · MRS Online Proceeding Library
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    ABSTRACT: Boron and antimony doped superlattices (DSLs) were implanted with arsenic at 40 keV to doses of 2×1014 cm−2, 5×1015 cm−2 and 2×1016 cm−2. Increasing the arsenic dose above 5×1015 cm−2 resulted in a reduction in the extent of arsenic transient enhanced diffusion (TED) following annealing at 700°C, 16 hr. Concurrent with this reduction in TED was a reduction in the number of free interstitials beyond the end-of-range, as measured by the boron diffusion enhancement in the doped superlattices. No enhancement in antimony diffusivity was observed in this region, indicating that vacancies play no direct role in the diffusion of arsenic in this region, although an indirect role for vacancies as recombination centers for mobile interstitials is not precluded by these experiments. We conclude that interstitials dominate arsenic diffusion in the end-of-range region and beyond. Interpretation of the DSL data in the projected range region is complicated by Fermi level and segregation effects and no definitive conclusion can be reached about the point defect populations in this region.
    No preview · Article · Jan 2011 · MRS Online Proceeding Library
  • R. Datta · V. Krishnamoorthy · L.P. Allen · R. Chandonnet · M. Farley · K. S. Jones
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    ABSTRACT: The effect of oxygen dose variation on the SIMOX SOI structure has been investigated extensively in this work. Keeping other implantation parameters constant, the dose has been varied from 0.2x1018cm–2 to 1.4xl018cm–2. Our studies show that a critical dose exists for a particular implant energy, below which a continuous buried oxide layer does not form. Further, the SiO2 precipitates enhance the pinning of defects in the as-implanted state which subsequently grow into threading dislocations. A dose window exists, where the dislocation density is a minimum.The oxygen depth distribution in the as-implanted and annealed state has been studied using SIMS. HRXRD measurements have been performed to reveal the strain state as a function of dose variation. The defect microstructure has been investigated using PTEM, XTEM and Secco Etching. AFM studies show the quality of the Si surface and Si/BOX (Buried OXide) interface roughness. This work gives us a fundamental understanding of the evolution of the defect microstructure and strain from the as-implanted to the annealed state using independent implantation parameter control.
    No preview · Article · Jan 2011 · MRS Online Proceeding Library
  • R. H. Thompson · V. Krishnamoorthy · J. Liu · K. S. Jones
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    ABSTRACT: P-type (100) silicon wafers were implanted with 28Si+ ions at an energy of 50 keV and to doses of 1 × 1015, 5 × 1015 and 1 × 1016 cm−2, respectively, and annealed in a N2 ambient at temperatures ranging from 700°C to 1000°C for times ranging from 15 minutes to 16 hours. The resulting microstructure consisted of varying distributions of Type II end of range dislocation loops. The size distribution of these loops was quantified using plan-view transmission electron microscopy and the strain arising from these loops was investigated using high resolution x-ray diffraction. The measured strain values were found to be constant in the loop coarsening regime wherein the number of atoms bound by the loops remained a constant. Therefore, an empirical constant of 7.7 × 10−12 interstitial/ppm of strain was evaluated to relate the number of interstitials bound by these dislocation loops and the strain. This value was used successfully in estimating the number of interstitials bound by loops at the various doses studied provided the annealing conditions were such that the loop microstructure was in the coarsening or dissolution regime.
    No preview · Article · Jan 2011 · MRS Online Proceeding Library
  • S.B. Herner · V. Krishnamoorthy · H.G. Robinson · K. S. Jones
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    ABSTRACT: The shrinkage in type II end-of-range dislocation loops was used to determine the relative flux of vacancies from the silicidation of titanium on silicon (100) wafers. A low temperature anneal (700°C 20 min.) in a forming gas ambient formed the initial silicide (approximately 750 angstrom thick), and several higher temperature anneals with the silicide intact and etched off followed to study the diffusion of the vacancies. The concentration of vacancies captured by the loops after a 900°C 60 minute post silicidation anneal was approximately 7.8 × 1013 /cm2 while the concentration after a 700°C 60 minute post silicidation anneal was only 9 × 1012 /cm2. Removal of the silicide prior to the high temperature post silicidation anneals resulted in fewer vacancies captured by the loops.
    No preview · Article · Jan 2011 · MRS Online Proceeding Library
  • S. B. Herner · V. Krishnamoorthy · K. S. Jones · T. K. Mogi · H.-J. Gossmann
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    ABSTRACT: The behavior of extrinsic dislocation loops in silicon was investigated by transmission electron microscopy. Loops were formed by an amorphizing implant and recrystallization anneal of Si wafers. Wafers were further annealed in either Ar or NH3. Wafers annealed in NH3 formed a thin (∼4 nm) SiNx film. The loops in samples in Ar showed a constant net number of interstitials bound by the loops, while those in samples annealed in NH3 showed a marked decrease. The results are explained by a supersaturation of vacancies recombining with the interstitials in loops. By integrating the measured difference between interstitials bound by the loops in samples annealed in Ar vs. NH3 over the distance from the surface to the loop layer, an estimate for the relative vacancy supersaturation is extracted. Comparison with estimates of vacancy supersaturations with nitridation from the change in Sb diffusivity show good agreement between the two methods.
    No preview · Article · Jan 2011 · MRS Online Proceeding Library
  • V. Krishnamoorthy · D. Venables · K. Moeller · K. S. Jones · J. Jackson

    No preview · Article · Jan 2011 · MRS Online Proceeding Library
  • J. Desroches · V. Krishnamoorthy · K. S. Jones · C. Jasper

    No preview · Article · Jan 2011 · MRS Online Proceeding Library
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    Hugo Saleh · Mark E. Law · Sushil Bharatan · Kevin S. Jones · Viswanath Krishnamoorthy · Temel Buyuklimanli
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    ABSTRACT: Boron, a p-type dopant, experiences transient enhanced diffusion (TED) via interstitials. The boron TED and {311} dissolution rates are explored as a function of implant energy dependence. Silicon implants of 1014/cm2 at various energies were used to damage the surface of a wafer with an epitaxially grown boron marker layer. Samples were annealed at 750 °C for 15-135 min to observe the diffusion exhibited by the marker layer and to correlate this with the dissolution of {311} type defects. The diffusion enhancement depends strongly on implant energy but the {311} dissolution rate is weakly dependent.
    Full-text · Article · Jul 2000 · Applied Physics Letters
  • Aaron D Lilak · Viswanath Krishnamoorthy · David Vieira · Mark Law · Kevin Jones

    No preview · Article · Jan 2000 · MRS Online Proceeding Library
  • P. H. Keys · R. Brindos · V. Krishnamoorthy · M. Puga-Lambers · K. S. Jones
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    ABSTRACT: The release of interstitials from extended defects after ion implantation acts as a driving force behind transient enhanced diffusion (TED). Implantation of Si + ions into regions of phosphorus-doped silicon provides experimental insight into the interaction of silicon interstitials and dopant atoms during primary damage annealing. The presence of phosphorus influences the morphology of secondary defects during initial nucleation. Transmission electron microscopy (TEM) is used to differentiate between defect types and quantify the interstitials trapped in extended defects. This analysis reveals that phosphorus results in a reduction of interstitials trapped in observable extended defects. The interstitial flux released from the implanted region is also affected by the phosphorus doping. This phenomenon is closely studied using secondary ion mass spectrometry (SIMS) to monitor diffusion enhancements of dopant layers. Shifts in diffused dopant profiles are correlated with the different morphologies of the extended defects and the decay of the silicon interstitial supersaturation. This correlation is used to understand the interaction of excess silicon interstitials with phosphorus atoms.
    No preview · Article · Jan 2000 · MRS Online Proceeding Library
  • V. Krishnamoorthy · M. Puga Lambers · Kevin S. Jones
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    ABSTRACT: This paper examines the effect of the surface on the recombination kinetics of point defects in silicon. In this experiment, arsenic ions are implanted into pre-amorphized silicon wafers at different energies to various doses. Point defects, specifically interstitials, are ejected when the arsenic concentration exceeds a critical value. These interstitials either cluster to form extended defects or diffuse to the surface where they are annihilated. A quantitative evaluation of the number of atoms contained in extended defects provides information on the effectiveness of the surface as an interstitial sink. The results of this study show that the surface is an effective sink for interstitials and that the number of interstitials annihilating at the surface increases with increasing surface proximity.
    No preview · Article · Jan 2000 · Defect and Diffusion Forum
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    R. Raman · M. E. Law · V. Krishnamoorthy · K. S. Jones · S. B. Herner
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    ABSTRACT: The effect of surface proximity on the dissolution of end-of-range dislocation loops in silicon was investigated by transmission electron microscopy (TEM). A layer of dislocation loops was formed at a depth of 2600 Å by annealing a Si wafer amorphized by a 1015 cm-2, 120 keV, and a 1015 cm-2, 30 keV dual Si+ implant for 30 min at 850 °C. The wafer was diced into 1 cm×1 cm pieces and polished by a chemical-mechanical polishing technique to decrease the loop depth to 1800 and 1000 Å. The samples were then furnace annealed at 900 and 1000 °C in N2 gas. Quantitative TEM analysis revealed that the density of small loops decreases as the loop band is brought closer to the surface. The flux of interstitials to the surface varied inversely with loop depth, indicating that the loop dissolution is diffusion limited. Assuming that the loops maintain a supersaturation of interstitials (CIL) around them, and by integrating the measured interstitial flux from the loop layer to the surface, the relative supersaturation of interstitials near the loop layer (CIL/CI*) was extracted 900 and 1000 °C.
    Full-text · Article · Mar 1999 · Applied Physics Letters
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    R. Raman · M. E. Law · V. Krishnamoorthy · K. S. Jones
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    ABSTRACT: The interactions between end-of-range dislocation loops and {311} defects as a function of their proximity were studied. The dislocation loops were introduced at 2600 Å by a dual 1×10<sup>15</sup>  cm <sup> -2 </sup>, 30 keV and a 1×10<sup>15</sup>  cm <sup> -2 </sup>, 120 keV Si <sup> + </sup> implantation into silicon followed by an anneal at 850 °C for 30 min. The depth of the loop layer from the surface was varied from 2600 to 1800 Å and 1000 Å by polishing off the Si surface using a chemical–mechanical polishing (CMP) technique. A post-CMP 1×10<sup>14</sup>  cm <sup> -2 </sup>, 40 keV Si <sup> + </sup> implantation was used to create point defects at the projected range of 580 Å. The wafers were annealed at 700, 800, and 900 °C, and plan-view transmission electron microscopy study was performed. It was found that the number of interstitials in {311} defects decreased as the projected range damage was brought closer to the loop layer, while the number of rectangular elongated defects (REDs) increased. Experimental investigation showed that REDs are formed at the end of range. It is concluded that the interstitials introduced at the projected range are trapped at the end of range. The REDs are formed due to the interactions between the interstitials and the pre-existing dislocation loops. © 1999 American Institute of Physics.
    Full-text · Article · Mar 1999 · Applied Physics Letters
  • R Raman · ME Law · V Krishnamoorthy · KS Jones

    No preview · Article · Jan 1999 · Applied Physics Letters
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    V. Krishnamoorthy · K. Moller · K. S. Jones · D. Venables · J. Jackson · L. Rubin
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    ABSTRACT: (001) CZ silicon wafers were implanted with As+ at 100 keV to a dose of 1×1015/cm2 in order to produce a continuous amorphous layer to a depth of about 120 nm. Furthermore, the implant condition was such that the peak arsenic concentration was below the arsenic clustering threshold. Subsequently, a second As+ or Ge+ implant was performed at 30 keV to doses of 2×1015/cm2, 5×1015/cm2 and 1×1016/cm2, respectively, into the as-implanted samples. All of the samples were annealed at 800 °C for 1 h. The second implant was designed to be contained within the amorphous region created by the initial implant. The second As+ implant was also designed to provide the additional arsenic needed to exceed the critical concentration for clustering at the projected range. Of the three samples with the dual As+ implant the clustering threshold was exceeded for the two lower doses while the SiAs precipitation threshold was exceeded at the highest dose. In the case of the dual As+/Ge+ implants the clustering and precipitation thresholds were not reached. Since arsenic and germanium are similar in mass the extent of damage created by these implants would be comparable. The implanted and annealed specimens were analyzed using secondary ion mass spectroscopy and transmission electron microscopy. The difference in the defect evolution and the transient-enhanced diffusion of arsenic beyond the end-of-range region between the As+ and Ge+ implanted and annealed samples was used to isolate the effects of arsenic clustering and precipitation. The results showed that point defects induced during clustering and/or precipitation did not contribute to the enhanced diffusion of arsenic although these defects did coalesce to form extended defects at the projected range. However, damage beyond the end-of-range region did cause enhanced diffusion of arsenic.
    Preview · Article · Dec 1998 · Journal of Applied Physics
  • J. Fitz-Gerald · S. Pennycook · H. Gao · V. Krishnamoorthy · J. Marcinka · W. Glenn · R.K. Singh
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    ABSTRACT: Particulate coatings have wide ranging applications in several new technologies such as flat-panel displays, sintering of advanced ceramics, rechargeable batteries, etc. In this paper, we show the feasibility of the pulsed laser ablation technique to make very thin, uniformly distributed and discrete coatings in particulate systems so that the properties of the core particles can be suitably modified. Presently, laser ablation techniques have been primarily applied to deposit thin films on flat substrate materials. To deposit discontinuous particulate coatings, the laser induced plume from the target comes in contact with an agitated bed of core particles. The pressure and nature of the background gas (inert or active) controls the cluster size of the nano particles in the laser plume. Experiments were conducted for laser deposition of Ag nano particles on Al2O3 and SiO2 core particles by pulsed excimer laser (wavelength = 248 nm and pulse duration = 25 nanosecond) irradiation of a Ag sputtering target The surface coverage and coating uniformities of the film were found to depend on the synthesis parameters (energy density, # laser pulses, gas pressure backfill gas, molecular weight) as well as the residence time of the core particles in the plume regime. The films were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), wavelength dispersive x-ray analysis (WDX), scanning transmission electron microscopy (STEM), and x-ray photoelectron spectroscopy (XPS).
    No preview · Article · Dec 1997 · MRS Online Proceeding Library
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    ABSTRACT: The thermal stability of tellurium in InP has been examined in samples doped with Te up to an electron concentration of 1.4 × 1020 cm−3. Annealing was conducted using rapid thermal annealing for a period of one minute at temperatures over the range 650–800°C. Secondary ion mass spectroscopy analysis showed virtually no change in the Te profile before and after annealing, even at the highest annealing temperatures. High resolution x-ray diffraction and Hall measurements revealed a general decrease in the lattice strain and carrier concentration for annealing temperatures above 650°C. No evidence of strain relief was found in the form of cross-hatching or through the formation of a dislocation network as examined by scanning electron microscopy or transmission electron microscopy (TEM). These results are most likely due to the formation of Te clusters, though such clusters could not be seen by crosssectional TEM.
    No preview · Article · Oct 1997 · Journal of Electronic Materials
  • S.B. Herner · V. Krishnamoorthy · A. Naman · K.S. Jones · H.-J. Gossmann · R.T. Tung
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    ABSTRACT: Titanium disilicide (TiSi2) films formed from varying compositions of co-deposited Ti and Si on a Si substrate and annealed in argon at 850°C have been characterized by Rutherford backscattering, Auger electron spectroscopy, transmission electron microscopy, atomic force microscopy, and high resolution X-ray diffraction. As-deposited films (TiSix) with x < 2 form a TiOxN1−x film on top of a TiSi2 film after annealing, while “Si-rich” (x > 2) film form TiSi2, with a poly Si film on top. This result is explained by the strong driving force of Ti to form an oxide or nitride with ambient gases while Si must diffuse through the growing film to form TiSi2. An “Si-rich” as-deposited composition (x > 2) results in less interface roughening between the TiSi2 film and Si substrate after annealing, as well as greater residual wafer curvature as compared to the other samples. The reduced wafer curvatures in the “Si-deficient” samples is attributed to the presence of the TiOxN1−x film which acts to counter the stress in the TiSi2 film.
    No preview · Article · Jun 1997 · Thin Solid Films
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    ABSTRACT: The effect of a thermally grown silicon nitride (SiNx) film on end-of-range extrinsic dislocation loops in a silicon substrate was investigated by transmission electron microscopy. A layer of extrinsic dislocation loops was formed by annealing a Si wafer amorphized by a Ge+ ion implant. A nitride film was grown on the Si by further annealing in ammonia (NH3) at 810 and 910 °C for 30–180 min. Wafers with a loop layer were also annealed in argon (Ar) at the same conditions as the NH3-annealed wafers to determine loop behavior in an inert environment. Samples annealed in NH3 had a significant decrease in the net number of interstitials bound by the loops, while those annealed in Ar showed no change. The results are explained by a supersaturation of vacancies caused by the presence of the nitride film, resulting in loop dissolution. By integrating the measured vacancy flux over the distance from the nitride/Si interface to the loop layer, we extract an estimate for the relative supersaturation of vacancies at 910 °C, CV/CV∗ ∼ 4, where CV is the concentration of vacancies and the asterisk denotes equilibrium. We rule out interstitial undersaturation-induced loop dissolution based on loop stability with temperature and oxidation-enhanced loop growth calculations. A comparison with estimated CV/CV∗ values from a previous report using the same processing equipment and parameters but monitoring the change in Sb diffusivity with nitridation shows excellent agreement.
    Full-text · Article · Jun 1997 · Journal of Applied Physics

Publication Stats

467 Citations
59.21 Total Impact Points

Institutions

  • 1991-2011
    • University of Florida
      • • Department of Materials Science and Engineering
      • • Department of Electrical and Computer Engineering
      Gainesville, Florida, United States
  • 1994
    • Cornell University
      • Department of Materials Science and Engineering
      Ithaca, New York, United States