P. H. Schmidt

Ion‐beam‐deposited polycrystalline diamondlike films

X‐ray and electron beam diffraction analyses have been carried out on thin films deposited from a beam of carbon ions. Results show that the films consist of a polycrystalline background of cubic diamond with a particle size of 50–100 A with single‐crystal regions up to 5 μm in diameter.

Structural and morphological investigation of the development of electrical conductivity in ion‐irradiated thin films of an organic material

Thin films of 3,4,9,10‐perylenetetracarboxylic dianhydride (PTCDA) develop low electrical resistivity ( 5×1...

Relationship between the conduction‐band discontinuities and band‐gap differences of InGaAsP/InP heterojunctions

We have measured the magnitude of the conduction‐band discontinuities at heterojunctions for several compositions of InGaAsP grown lattice matched on InP. We find that the conduction‐band discontinuity (ΔEc) is related to the difference in band gaps (ΔEg) between the InGaAsP and InP layers via ΔEc =0.39(ΔEg). Thus, 40% of the band‐gap difference lies in the conduction band of this material system. The measurements were made on a series of composition of InGaAsP spanning the alloy range from In0.53Ga0.47As (with energy gap Eg =0.75 eV) to InP (Eg =1.35 eV) using capacitance‐voltage techniques. Depletion deep into the semiconductor layers was facilitated by the formation of organic‐on‐inorganic semiconductor contact barriers on the InGaAsP surface.

Ion‐beam‐induced conductivity in polymer films

Polymer films darken upon irradiation with energetic ion beams. At high doses (1016–1017 cm−2) of 2‐MeV Ar+ ions, the resistivity of these insulating films decreases dramatically to 3.5×10−3 Ω cm. Furthermore, over a wide range of doses (1014–1015 cm−2) these films exhibit a temperature‐dependent resistivity characteristic of carrier transport via hopping between isolated conducting islands. Rutherford backscattering measurements indicate that while a substantial amount of the carbon is retained in the film, other constituent elements are lost. Raman spectra show that the films are highly disordered at large ion doses.

Optical and electrical properties of ion‐beam‐irradiated films of organic molecular solids and polymers

Thin films of several nonpolymeric and polymeric organic compounds become optically dark and electrically conducting on irradiation with energetic particle beams. Using 2‐MeV Ar+ ion beam irradiation, we have generated conducting patterns in otherwise high‐resistivity, organic thin films among which are 3, 4, 9, 10‐perylenetetracarboxylic dianhydride, 1, 4, 5, 8‐napthalenetetracarboxylic dianhydride, and Ni phthalocyanine. The room‐temperature resistivity of the films changes by 14 orders of magnitude from its as‐deposited value of ρ>1010 Ω cm to ρ=5×10−4 Ω cm at ion doses of 1017 cm−2. The temperature (T) dependence of the resistivity follows ρ(T)∝exp(+(T0/T)1/2 ) over a wide range of dose and temperature. The characteristic temperature T0 is found to be a function of dose. The observed behavior of ρ(T) is consistent with charge transport due to hopping between isolated, conducting islands. The dependence on ion energy, ion species, and ion dose rate has been examined. The effectiveness of an ionic speci...

n‐indium tin oxide/p‐indium phosphide solar cells

n‐indium tin oxide/p‐indium phosphide (n‐ITO/p‐InP) solar cells have been prepared by ion‐beam deposition of indium tin oxide on p‐InP single‐crystal substrates. The cells have a solar power conversion efficiency of 14.4% at air mass 2 (AM2) when provided with antireflection coatings.

Carbon films with relatively high conductivity

The pyrolysis of organic dianhydrides (e.g., 3,4,9,10‐perylenetetracarboxylic dianhydride) in an evacuated system results in the loss of hydrogen, CO, and CO2 and the deposition of a chemically inert, metallic‐appearing mirrolike film. The films are highly conducting (σRT250 Ω−1 cm−1) and can evidence either metallic or semiconducting behavior, depending on the preparation temperature. Superconducting films are obtained when niobium is used as a dopant. Preparation of films on doped silicon semiconductor chips results in the formation of p‐n junctions. ESR spectra exhibit a moderately strong line at g=2.0025. The resonance intensity remains almost constant to 20 °K, characteristic of a highly delocalized spin system.

Solar-cell characteristics and interfacial chemistry of indium-tin-oxide/indium phosphide and indium-tin-oxide/gallium arsenide junctions

The preparation of indium‐tin‐oxide (ITO)/p‐InP and ITO/p‐GaAs solar cells via ion‐beam deposition, rf sputtering, and magnetron sputtering of ITO onto single‐crystal InP and GaAs substrates is described. The properties of these solar cells are strongly affected by the fabrication conditions and are related to chemical modifications of the junctions. The solar power conversion efficiencies at air mass 2 of ITO/p‐GaAs and ITO/p‐InP solar cells are ?5 and ?14.4%, respectively.

REDETERMINATION OF THE NONLINEAR OPTICAL COEFFICIENTS OF Te AND GaAs BY COMPARISON WITH Ag3SbS3

The nonlinear optical coefficients d11(Te) and d14(GaAs) have been determined relative to d+(Ag3SbS3), pyrargyrite, in second harmonic generation (SHG) experiments at 10.6μ. Based on an absolute value for d+(Ag3SbS3) previously determined, we find that d11(Te) = (22±7) × 10−7 esu, and d14(GaAs) = (3.2±1) × 10−7 esu. The value for Te is significantly less than the previously accepted values.

The preparation, spectral properties, and X-ray structural features of 2,3-naphthalocyanines

Abstract We have prepared a series of 2,3-naphthalocyanine (H2NPc) compounds and examined their spectroscopic properties. All of them can be vacuum sublimed as thin films which absorb strongly in the near infrared and thus make them potentially useful as optical data recording media. In addition, we have measured the electrical resistivities, at room temperature, of several of the compacted 2,3-naphthalocyanines and find them to be semiconductors. Doping with bromine vapor enhances the conductivities only slightly (H2NPc actually becomes more resistive).