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Advanced input/output (I/O) technology is reported for leading-edge system on a chip (SoC) applications, including high-speed I/O and RF circuits. Our device having a laterally modulated channel shows sufficient reliability even at 3.3 V operation with the same size as a conventional 2.5 V device. Since this technology also improves current drivability, the layout area of an I/O circuit block can be reduced down to 55% because of a reduced total gate width. Moreover, a metal-on-gate (MOG) option has been developed for RF applications, and an fmax of 55 GHz was achieved.

Hemispherical Si quantum dots have been self-assembled on thermally grown 3.2-nm-thick SiO2/p-Si(100) by low-pressure chemical vapor deposition of silane. The charging states of the Si quantum dots have been detected as surface potential changes by using an atomic force microscopy/Kelvin force probe method. From the relationship between the measured surface potential changes and the charging energy of a single dot, the number of electrons retained in a dot has been estimated to be one. Furthermore, it is found that electron extraction from neutral dots can be achieved to create a hole at each dot.

The repetition rate of a regeneratively and harmonically mode-locked fiber laser at 10 GHz has been successfully stabilized by using an offset locking technique. The clock frequency which deviates from a standard frequency is converted into a voltage signal using a double balanced mixer and an F/V converter. This voltage signal, after passing through electrical control units, is fed back to the PZT on which part of the fiber cavity is wound. In this way, a repetition-rate stability of more than 10-9 was achieved.

A continuous wave suppressed, uniformly repetitive pulse train as short as 136–145 fs has been successfully generated at a wavelength of 1.55 µ m from a new type of femtosecond erbium-doped fiber laser with nonlinear polarization rotation. The 145 fs pulse was shortened to 52 fs by using soliton narrowing and high order soliton compression. Soliton narrowing was achieved by amplifying the soliton pulse with an erbium-doped fiber amplifier, and a short length of dispersion-flattened fiber was used for further compressing the soliton.

The lasing characteristics of an erbium-doped fiber laser with a nonlinear amplifying loop mirror (NALM) were investigated in detail. The NALM was pumped by 1.48 µm InGaAsP laser diodes and an output pulse as short as 124 fs was obtained at 1.56 µm. The 124-fs pulse was shortened to 50 fs by using adiabatic soliton narrowing and high order soliton compression. Soliton narrowing was achieved by amplifying the soliton pulse adiabatically with an erbium-doped fiber amplifier, and a short length of dispersion-flattened fiber was used for soliton compression. Soliton narrowing enabled us to succeed in generating a 98-fs pulse directly from a modified erbium-doped fiber laser.

Thicknesses of amorphized layers on Si(100), (110), and (111) wafers resulting from 45° sputter cleaning with Ar+ in the energy range from 1 to 5 keV have been determined by analyzing secondary electrons induced by 40 MeV O5+ under channeling incidence conditions. Thickness is independent of wafer orientation and increases approximately linearly with Ar+ energy up to 35±5 Å for 5 keV Ar+. Since in the analysis an ambiguity associated with the surface condition of undamaged crystal is eliminated, this method is extremely useful for investigating nanometer-thick disordered surfaces.

High-quality images of the ion-beam shadowing effect in single crystals have been constructed with keV secondary electrons induced by 60-MeV oxygen ions. Under a high count rate (∼104 counts/s) of the electron yield, the time needed to measure the electron yield for about 3000 tilt angles, from which the shadowlng pattern for a 1°×1° angular space (for two independent tilts) was obtained, was 40-60 min when accumulating the electron yield up to 5000-10000 counts per tilt angle. This practical method for visualizing the crystal lattice is suitable for characterization of crystalline materials.

The gain characteristics of an erbium-doped fiber amplifier pumped in the 800 nm band have been investigated in detail. The fiber has a dual shape core and the erbium ions are doped only in the inner core to improve the pumping efficiency. The most efficient pumping wavelength is around 820 nm which is determined by the trade off between the decrease in excited state absorption and the decrease in the absorption coefficient. This pumping wavelength makes it possible to achieve an optical gain as high as 40 dB. The noise figures of Er3+-doped fiber amplifiers pumped in the 800 nm band are 4-5 dB in the 1.5 µm signal wavelength region.