The effect of impurity coimplantation in MeV erbium‐implanted silicon is studied. A significant increase in the intensity of the 1.54‐μm Er3+ emission was observed for different coimplants. This study shows that the Er3+ emission is observed if erbium can form an impurity complex in silicon. The influence of these impurities on the Er3+ photoluminescence spectrum is demonstrated. Furthermore we show the first room‐temperature photoluminescence spectrum of erbium in crystalline silicon.

Impurity enhancement of the 1.54‐μm Er3+ luminescence in silicon

Implantation of MeV erbium ions into micron‐thick silica and phosphosilicate glass films and 1200‐A‐thick Si3N4 films is studied with the aim of incorporating the rare‐earth dopant on an optically active site in the network. Implantation energies and fluences range from 500 keV to 3.5 MeV and 3.8×1015 to 9.0×1016 ions/cm2. After proper thermal annealing, all implanted films show an intense and sharply peaked photoluminescence spectrum centered around λ = 1.54 μm. The fluorescence lifetime ranges from 6 to 15 ms for the silica‐based glasses, depending on annealing treatment and Er concentration. Silicon nitride films show lower lifetimes, in the range <0.2–7 ms. Annealing characteristics of all materials are interpreted in terms of annealing of ion‐induced network defects. These defects are identified using photoluminescence spectroscopy at 4.2 K. Concentration quenching, diffusion and precipitation behavior of Er is also studied.

Optical doping of waveguide materials by MeV Er implantation

The optical activation, excitation, and concentration limits of erbium in crystal Si are studied. Preamorphized surface layers of Czochralski‐grown (Cz) Si(100), containing 1.7×1018 O/cm3, were implanted with 250 keV Er at fluences in the range 8×1011–8×1014 cm−2. After thermal solid‐phase epitaxy of the Er‐doped amorphous layers at 600 °C, Er is trapped in the crystal at concentrations ranging from 3×1016 to 7×1019 Er/cm3, as measured by secondary‐ion‐mass spectrometry. Photoluminescence spectra taken at 77 K show the characteristic Er3+ intra‐4f luminescence at 1.54 μm. Photoluminescence excitation spectroscopy shows that Er is excited through a photocarrier‐mediated process. Rapid thermal annealing at 1000 °C for 15 s increases the luminescence intensity, mainly due to an increase in minority‐carrier lifetime, which enhances the excitation efficiency. Luminescent Er forms clusters with oxygen: the maximum Er concentration that can be optically activated is determined by the O content, and is (3±1)×1017...

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Erbium in crystal silicon: Optical activation, excitation, and concentration limits

The optical absorption of thermally evaporated copper phthalocyanine (CuPc) was studied in the UV-VIS-NIR region. The absorption spectra recorded in the UV-VIS region show two well-defined absorption bands of the phthalocyanine molecules, namely, the Soret ( B ) and the Q -band . The Q -band shows its characteristic splitting (Davydov splitting) of the main absorption peak in the metal phthalocyanine correlates with the relative tendencies of the metal to out-of-plane bonding. Some of the important spectral characteristics such as the molar extinction coefficient (e molar ), the oscillator strength ( f) , the electric dipole strength ( q 2 ) and absorption half-bandwidth (Δ λ ) of the principle optical transitions were evaluated. The analysis of the spectral behavior of the absorption coefficient α in the absorption region revealed two indirect allowed transitions with corresponding energies 2.95±0.03 and 1.55±0.02 eV. The spectra of the infrared absorption allow characterization of vibration modes for the powder, as-deposited material and thin films of CuPc annealed at 423 K for two hours. Discussion of the obtained results and their comparison with the previous published data are also given.

Optical absorption studies of copper phthalocyanine thin films

This chapter focuses on the molecular electronic, molecular magnetic, and molecular iono-electronic devices to target the development of novel electro-optical information-processing systems. The significance of porphyrins can be envisaged from their involvement in most important processes of natural life. Sandwich-type, in particular, bis[(na)phthalocyaninato] metal complexes with long alkyl substituents are among the most promising species of novel liquid crystal materials. The synthesis of covalently linked aggregates of porphyrinato metal sandwiches and quinones as realized for the monomeric porphyrins that seems to be a mammoth undertaking. The synthesis of multiple-decker porphyrinato and phthalocyaninato metal complexes are expected to show more interesting electronic characteristics, and more effective π–π interactions than the corresponding coordination metallopolymers, which seems to be another approach to lead to good molecular conductors. It must be pointed out that the research to fabricate such sandwich type metal phthalocyaninato and porphyrinato complexes into molecular electronic devices still remains undeveloped at the present stage. They are sure to play an important role in developing new electronic, iono-electronic, or optical devices for information processing.

Chapter 2 – Sandwich-Type Phthalocyaninato and Porphyrinato Metal Complexes

Spectroscopic and structural studies of scandium diphthalocyanine films

Erbium-implanted silicon layers have been studied both by secondary ion mass spectrometry (SIMS) and by photoluminescence (PL). The SIMS analysis shows the erbium redistribution inside the substrate following the rapid thermal annealing and the implantation energy. The PL spectra present a maximum intensity at 1.54 μm corresponding to the Er3+ emission. The intensity depends on the implantation dose.

1.54 μm photoluminescence of erbium-implanted silicon

Erbium impurities were implanted in indium phosphide. The 2 K, 77 K and 300 K photoluminescence spectra show, after annealing at high temperature, the main erbium emission centered at 1.536μm. The variation of this Er-peak luminescence is studied as a function of the implanted dose, the annealing temperature and the annealing duration.

Behaviour of Erbium implanted in InP

Silicon is widely used for n-doping of GaAs/(Al, Ga)As layered structures grown by molecular beam epitaxy or metallo-organic chemical vapour phase deposition for high speed and opto-electronic devices, so the determination of Si doping levels in these structures is of primary importance. The secondary ion mass spectrometry technique has been revealed as a very powerful method for such a determination. But, in this particular case, some difficulties are encountered at low doping levels because of the presence of ions interfering with the main silicon isotope at mass 28. This paper deals with the search for satisfactory experimental conditions for such a silicon analysis under caesium primary ion bombardment, the main requirements being the detection limit and the depth resolution. It will be shown that AIH molecular ions are the interfering species and two approaches have been explored to avoid this interference: use of high mass resolving power facilities of a double focusing mass spectrometer, or experimentation at low vacuum conditions. A compromise is ineviatable between maximum sensitivity in the 1–2 1015 cm−3 range by detecting negative secondary ions and good depth resolution, equal to about, 40 A, by using positive secondary ion collection. The ultimate performances of the technique are limited by the silicon surface segregation process and factors like the initial surface morphology of the samples, the flatness, and parallelism with the surface, of the crater bottoms and the beam induced roughness.

M. Salvi

Papers

Spectroscopic and structural studies of scandium diphthalocyanine films

1.54 μm photoluminescence of erbium-implanted silicon

Behaviour of Erbium implanted in InP

SIMS analysis, under caesium bombardment, of Si in GaAs/(Al, Ga) as superlattices: Detection limit and depth resolution

Spatial investigation of an iron-doped indium phosphide ingot