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15 Mar 2002

Volume 91, Issue 6, pp. 3495-3945

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Hydrogen detection on bare SiO2 between metal gates

D. Filippini and I. Lundström

J. Appl. Phys. 91, 3896 (2002); http://dx.doi.org/10.1063/1.1450025 (8 pages) | Cited 6 times

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Metal–oxide–semiconductor capacitors with gates of Pd and Au forming a wedge of bare SiO2 between them are described. It is observed that the sensitivity to H2 in the wedge is larger than on the outside of the metal gates due to the different distribution of potential determined by the geometrical constraints. The local response of the surface is obtained through the use of a scanning light pulse technique (SLPT), showing photocurrent versus voltage curves shifted to more negative voltages upon exposure to hydrogen. Within the wedge there is a two-dimensional photocurrent pattern composed of two splitting photocurrent peaks, whose separation depends on the distance between Au and Pd contacts, and on the composition of the ambient. The transient response in the wedge is comparable to that of Pd gates and the possibility of detecting hydrogen (or other molecules) by measuring on the bare insulator surface provides new possibilities for the use of field-effect structures for gas sensing. A semiempirical model describing the SLPT response for this particular geometry, conforms to experimental features, and highlights the sensitivity of the distribution of potential in the wedge to the density of charges induced on the semiconductor surface. © 2002 American Institute of Physics.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
84.32.Tt Capacitors
85.30.Tv Field effect devices
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
72.40.+w Photoconduction and photovoltaic effects

Remote-plasma chemical vapor deposition of conformal ZrB2 films at low temperature: A promising diffusion barrier for ultralarge scale integrated electronics

Junghwan Sung, Dean M. Goedde, Gregory S. Girolami, and John R. Abelson

J. Appl. Phys. 91, 3904 (2002); http://dx.doi.org/10.1063/1.1436296 (8 pages) | Cited 16 times

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High-quality ZrB2 thin films have been deposited at substrate temperatures as low as 300 °C by a new method: remote hydrogen-plasma chemical vapor deposition from the single-source precursor Zr(BH4)4. Carrying out the deposition in the presence of atomic hydrogen generates films with properties that are far superior to those deposited by purely thermal methods; the latter are boron-rich, oxidize readily in air, and adhere poorly to the substrates. In contrast, the films generated at a substrate temperature of 300 °C in the presence of atomic H have a B/Zr ratio of 2, a resistivity of 40 μΩ cm, an oxygen content of ⩽4 at. %, and are fully conformal in deep vias. A 20 nm thick amorphous film of ZrB2 on c-Si(001) prevents Cu indiffusion after 30 min at 750 °C. We propose that the beneficial effects of atomic hydrogen can be attributed to promoting the desorption of diborane from the growth surface. © 2002 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.35.Fx Diffusion; interface formation
52.77.Dq Plasma-based ion implantation and deposition
85.40.Sz Deposition technology
68.55.-a Thin film structure and morphology

Patterned heteroepitaxial processing applied to ZnSe and ZnS0.02Se0.98 on GaAs (001)

X. G. Zhang, A. Rodriguez, P. Li, F. C. Jain, and J. E. Ayers

J. Appl. Phys. 91, 3912 (2002); http://dx.doi.org/10.1063/1.1446227 (6 pages)

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We have demonstrated the patterned heteroepitaxial processing (PHP) approach for the removal of threading dislocations (TDs) from ZnSe and ZnS0.02Se0.98 on GaAs (001). PHP involves the growth of a continuous heteroepitaxial layer followed by postgrowth patterning and annealing. We found that the basic mechanism of TD removal by PHP is thermally activated dislocation motion in the presence of sidewalls. By studying the temperature dependence we showed that the activation energy for the annealing process (∼0.7 eV in ZnSe on GaAs) is consistent with dislocation motion by glide. We showed that there is a minimum mesa thickness required for the complete removal of TDs by PHP (∼3000 Å for 70 μm×70 μm mesas of ZnSe on GaAs). This is because the lateral forces acting on TDs are proportional to the mesa thickness. We also conducted a preliminary study of the mismatch dependence of PHP. Our results suggest that PHP removes TDs more effectively in the higher lattice mismatch system ZnSe/GaAs (001) than in the lower lattice mismatch system ZnS0.02Se0.98/GaAs (001). This is expected based on the mismatch dependence of the line tension forces in the misfit segments of dislocations. © 2002 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.05.Dz II-VI semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.A- Nucleation and growth
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
61.72.Cc Kinetics of defect formation and annealing

Electron field emission from diamond-like carbon films and a patterned array by using a Ti interfacial layer

D. S. Mao, X. H. Liu, X. Wang, and W. Zhu

J. Appl. Phys. 91, 3918 (2002); http://dx.doi.org/10.1063/1.1448405 (4 pages) | Cited 12 times

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Electron field emission from diamond-like carbon (DLC) films deposited on Si, Ti/Si, and Au/Si substrates by a filtered arc deposition technique was studied. As compared to DLC/Si and DLC/Au/Si, electron field emission from DLC/Ti/Si was enhanced, showing an increased emission current density and emission site density (∼1.2×103/cm2). An emission site density up to 2.2∼2.2×103/cm2 was obtained after the DLC/Ti/Si had been annealed at 430 °C for 0.5 h. A patterned DLC/Ti/Si array fabricated by the oxygen reactive ion beam etching technique showed further field emission enhancement. An emission site density up to 3.2∼3.5×103/cm2 and a threshold field as low as 2.1 V/μm were achieved. It was shown that the low potential barrier at the interface and high local geometric electric field enhancement around the edges produced by reactive ion beam etching were possible causes of the enhancing effects. It could also be explained by Geis’ metal-diamond-vacuum triple junction emission mechanism. © 2002 American Institute of Physics.
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79.70.+q Field emission, ionization, evaporation, and desorption
81.65.Cf Surface cleaning, etching, patterning
61.72.Cc Kinetics of defect formation and annealing
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.05.U- Carbon/carbon-based materials
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