V. Krishnamoorthy

University of Florida, Gainesville, Florida, United States

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Publications (36)62.13 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.
    MRS Online Proceeding Library 01/2012; 438.
  • R. H. Thompson, V. Krishnamoorthy, J. Liu, K. S. Jones
    MRS Online Proceeding Library 01/2011; 378.
  • J. Desroches, V. Krishnamoorthy, K. S. Jones, C. Jasper
    MRS Online Proceeding Library 01/2011; 469.
  • S.B. Herner, V. Krishnamoorthy, H.G. Robinson, K. S. Jones
    MRS Online Proceeding Library 01/2011; 337.
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    ABSTRACT: Scandium oxide was deposited epitaxially on (0001) GaN via gas-source molecular beam epitaxy (GSMBE) using elemental Sc and an electron cyclotron resonance (ECR) oxygen plasma. HXRD indicated that the Sc2O3 has a lower defect density than similarly prepared films of Gd2O3. The scandium oxide was atomically smooth, with a rms roughness of 0.5–0.8 nm, and was uniform in stoichiometry as measured by Auger electron spectroscopy (AES) depth profiling. An interface state density of mid 1011 eV—1 cm—2 was determined from capacitance–voltage profiling using the Terman method. This interface state density was roughly a factor of five lower than that obtained from similar diodes made from SiO2 on GaN.
    physica status solidi (a) 11/2001; 188(1):239 - 242. · 1.21 Impact Factor
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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.
    MRS Online Proceeding Library 01/2000; 610.
  • Aaron D Lilak, Viswanath Krishnamoorthy, David Vieira, Mark Law, Kevin Jones
    MRS Online Proceeding Library 01/2000; 610(1).
  • V. Krishnamoorthy, M. Puga Lambers, Kevin S. Jones
    Defect and Diffusion Forum 01/2000;
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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.
    Applied Physics Letters 01/2000; 77. · 3.52 Impact Factor
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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.
    Applied Physics Letters 03/1999; · 3.52 Impact Factor
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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.
    Applied Physics Letters 01/1999; 74. · 3.52 Impact Factor
  • R Raman, ME Law, V Krishnamoorthy, KS Jones
    Applied Physics Letters 01/1999; 74(5):700-702. · 3.52 Impact Factor
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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.
    Journal of Applied Physics 12/1998; 84(11). · 2.19 Impact Factor
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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).
    MRS Online Proceeding Library 12/1997; 526.
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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.
    Journal of Electronic Materials 10/1997; 26(11):1283-1286. · 1.68 Impact Factor
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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.
    Thin Solid Films 06/1997; · 1.87 Impact Factor
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    ABSTRACT: Transient enhanced diffusion (TED) of boron in silica after low energy boron implantation and annealing was investigated using boron-doping superlattices (DSLs) grown by low temperature molecular beam epitaxy. Boron ions were implanted at 5, 10, 20, and 40 keV at a constant dose of 2×1014/cm2. Subsequent annealing was performed at 750 °C for times of 3 min, 15 min, and 2 h in a nitrogen ambient. The broadening of the boron spikes was measured by secondary ion mass spectroscopy and simulated. Boron diffusivity enhancement was quantified as a function of implant energy. Transmission electron microscopy results show that 〈311〉 defects are only seen for implant energies ⩾10 keV at this dose and that the density increases with energy. DSL studies indicate the point defect concentration in the background decays much slower when 〈311〉 defects are present. These results imply there are at least two sources of TED for boron implants (B-I): short time component that decays rapidly consistent with nonvisible B-I pairs and a longer time component consistent with interstitial release from the 〈311〉 defects. © 1997 American Institute of Physics.
    Journal of Applied Physics 02/1997; 81(4):1656-1660. · 2.19 Impact Factor
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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.
    Journal of Applied Physics 01/1997; 81:7175-7180. · 2.19 Impact Factor
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    Jingwei Xu, V. Krishnamoorthy, Kevin S. Jones, Mark E. Law
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    ABSTRACT: Transient enhanced diffusion (TED) results from implantation damage creating enhanced diffusion of dopants in silicon. This phenomenon has mostly been studied using boron marker layers. We have performed an experiment using boron, phosphorus, and dislocation markers to compare TED effects. This experiment shows that phosphorus is enhanced significantly more than boron during damage annealing. Dislocation growth indicates that a number of interstitials greater than the damage dose is captured during these anneals. The time to saturate the dislocation growth agrees well with phosphorus diffusion saturation, and is greater than the boron saturation. © 1997 American Institute of Physics.
    Journal of Applied Physics 12/1996; 81(1):107-111. · 2.19 Impact Factor
  • S. B Herner, V Krishnamoorthy, K. S Jones
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    ABSTRACT: The behavior of end-of-range dislocation loops have been used to study the flux of point defects in Si after the formation of a TiSi2 film. Extrinsic dislocation loops were formed in Si which then had 30 nm of Ti deposited and annealed to form TiSi2. Control samples with loops but without a TiSi2 film were annealed concurrently without a TiSi2 film to provide a comparison. The density of the interstitials bound by the loops was measured by plan view TEM. Enhanced loss of interstitials bound by the loops in the silicided samples indicate a vacancy supersaturation caused by the presence of the TiSi2 film. By assuming a constant flux of vacancies from the TiSi2Si interface to the layer of dislocation loops, we measure CVDV values, where CV = concentration of vacancies and DV = diffusivity of a vacancy. By using a literature estimate of CV∗DV, where CV∗ = equilibrium population of vacancies, we derive CVCV∗ ∼ 1.2 for Si annealed with a TiSi2 film, which is in substantial agreement with the value from a previous study.
    Applied Surface Science 12/1996; 103(4):377-382. · 2.54 Impact Factor

Publication Stats

372 Citations
62.13 Total Impact Points

Institutions

  • 1991–2000
    • University of Florida
      • • Department of Materials Science and Engineering
      • • Department of Electrical and Computer Engineering
      Gainesville, Florida, United States
  • 1994–1996
    • Cornell University
      • Department of Materials Science and Engineering
      Ithaca, NY, United States