Kenzo Sato

The Nf-R curve for the gap lattice band and the electron spin reversion effect under a weak magnetic field

Abstract The surface sensitivity of gallium phosphide was studied by measurement of the infrared fundamental lattice band profile, and the following effects are explained using the Nf-R curve which was derived successfully from the classical dispersion relation. For n-type material, with tellurium and sulphur impurities, the reflection profile of the (100)a plane is well explained by classical dispersion analysis, but that of the (100)b plane is impossible to treat since the profile is sensitivity modified by the treatment. In particular, under a weak magnetic field the change of reflectivity at the lattice band region (380 cm -1 ) is reversible with the polarity of the field. Classically, these effects are explained as being induced by the variation of the oscillator strength f in the Nf-R curve, relating to the spin reversion effect of the lone-paired electrons. Also, in the linear process of the interaction of the surface donor electrons and IR radiation, the statistical variation of the spin magnetic moment and hence excitation/transition probability is considered as an origin of the spin reversion effect. This effect is also verified by measurements of the reflectivity of ferromagnetic substances such as iron in the visible region.

Infrared optical properties of a silica layer on silicon under weak modulation fields

Abstract The optical properties of a silica layer grown on a silicon substrate were investigated using IR modulation spectroscopy. The investigation was based on studies of electro-optical and magneto-optical effects in metals. The modulation was induced by electrical current flow, by a weak magnetic field, by a weak dynamic stress or by an electric field. We found that the hopping conduction of carriers at the interface was closely related to the SiO and SiSi bonds. The modulation of the reflection spectrum produced by the application of a weak stress was more marked than the other types of modulation. The origins of these effects are discussed quantum mechanically.

Fine interaction of the conduction electrons in copper

Abstract From analysis of the variation in the reflectivity induced in the IR reflection spectra of copper surfaces we found that the effect which is dependent on current flow is more sensitive than the effect induced by magnetic perturbation. With regard to the sensitivity of the solid surface we discuss the degree of looseness of the spin-oriented lone-pair electrons as estimated from the Nf-R curve; this suggests that in the case of current flow the transition probability of the randomly oriented lone-pair electrons is dominant rather than the effect due to the spin-oriented lone-pair electrons is In contrast, for an applied magnetic field the transition probability of the spin-magnetic part is dominant rather than the Coulomb part. So far as the region of surface sensitivity is concerned, the magnetic, electrical and optical properties are reasonably explained by assuming a variation in the density of the lone-pair electrons which are distributed in the 3d-4s mixed levels.

Fine interaction of the surface electrons in copper

Abstract From IR reflection measurements of copper surfaces it was found that the spectra change according to the specimen face and treatment and that they are of three types. One is a step increasing reflection spectrum with three fine series in the 2.5–50 μm region. The second type of profile consists of a broad band in the 7–16 μm region and a steep reflection edge in the 20–30 μm region. The third is a combination of the first two types of profile. The dependence of these profiles on a weak magnetic field was studied and the magnetic-sensitive profile in the step series is discussed. The magnetic sensitive/insensitive profile in the step series and in the reflection edge is attributed to the loosely/tightly bound lone-pair electrons distributed in the 3d electron and hybrid electron bands. The properties of the reflection edge of copper are compared with the plasma edge profile of heavily doped silicon.

IR optical susceptibilities of the surface electrons in GaAs under weak modulation fields

Abstract The IR optical susceptibilities of the surface electrons in the (001) face of GaAs doped with tellurium were investigated. In particular, their dependence on thermal agitation (23–250 °C), carrier conduction (0–0.1 A mm-1), magnetic field (0–20G), electric field (0–30 V mm-1) and applied positive stress (0–200 gf cm-2) perpendicular to the surface was studied. It was found that the optical susceptibilities of the Coulomb electrons are most sensitive and depend on the polarity of the Biot-Savart field induced. The susceptibility of the thermally agitated electrons is also sensitive, but the susceptibilities of other electrons are not so sensitive. In fact, the optical susceptibilities are almost proportional to the density of these electrons. These susceptibilities are well explained theoretically on the basis of spin quantum mechanics.

The electro-optical effect of the coulomb electrons and the magneto-optical effect of the magnetic electrons in the surface of heavily doped silicon

Abstract From precise measurements of the soft Zeeman effect and the electro-optical effect at the plasma edge of heavily doped Si(111) it is found that the excess electrons are sensitive to the carrier conduction rather than to the applied magnetic field, depending on the forward or backward current. For the forward current the Coulomb electrons in shallow conduction bands are more optically sensitive, but for the backward current the Coulomb electrons which are distributed to the region of the reflection minimum at the shorter wavelength side of the plasma edge are the more optically sensitive. Also, the fine step series in the profile of the plasma edge similar to that for metals is shown to be Eij = giN + Agj(I, H)M where gi = 1.34 × 10−2 eV, N = 1, 2,…, 10, A = 1.28 × 10−1 eV, gj(I, H) = 5 - 10 meV and M = 1, 2,…, 5 for silicon with an impurity concentration of 5 × 1020 cm−3.

Spin orientation effects of shallow electrons induced by magnetization in transition metal surfaces

Abstract From infrared reflection measurements of transition metal surfaces it has been found that the profile is sensitively changed by both magnetization and demagnetization. In particular, the longer wavelength side of the reflection edge induced at the 7 – 15 μm region by magnetization with about 300 G is attributed to shallow electrons which are strongly spin oriented. The shorter wavelength side of the edge is due to mixed electrons which are rather weakly spin oriented. The effect of the three types of edge distribution indicates that the interface between the continuum and the mixed level is sensitive to the degree of magnetization; the degree of variation of the magnetic oscillator is estimated from the Nf-R curve to be within the range 10 21 cm -3 - 10 24 cm -3 .

The Stark effect induced in the IR lattice bands of titanium oxide

Abstract Measurements of the Stark effect induced in the IR lattice bands of the Ti-O oscillator in titanium oxide (TiO2) demonstrate that the intensity of reflection from electrically polarized oscillators depends sensitively on induced polarization effects. The degree of polarization was estimated from Nf-R curves where N is the oscillator concentration of the Ti-O bond, f is the oscillator strength and R is the reflectivity maximum of the lattice band. The dependence of the effective charge of the oscillator on the applied electric field is found to be e ∗ (E)=e 0 ±°e 0 where e0=3.68×10-10 e.s.u. and °e0=2.2×10-9V2−1.1×10-6V e.s.u. The dipole moment is estimated to increase from 7.34 to 7.78 debyes.

The IR electromagnetic effect induced in the fine step bands of the (001) face of GaAs(Te) by applying an alternating field

Abstract The optical sensitivity of the excess impurity lone-pair electrons is discussed on the basis of the values of the IR reflection integral which were derived from the plasma edge profile of the (001) face of GaAs(Te) for eight levels of dopant concentration. From the analysis of the variation in the reflectivity including annihilation and creation of some fine step bands induced by applying an alternating electromagnetic field with frequency f = A × 10 m−1 ( m = 1, 2, …, 7) parallel to the direction, we estimate that this sensitive effect may be induced primarily by the dynamical variation of the matrix elements of these oscillators, the values of which are determined by the dipole moments and oscillator concentrations. By using the Nf-R relations of the fine step bands measurable at 274 cm -1 , 290 cm -1 and 315 cm -1 , the degree of variation in the effective oscillator concentration and the effective charge are estimated and reasonable values are obtained, by comparison with the Born effective charge the dipole-moments were determined. The step property of the nine fine step bands superimposed on the fundmental lattice band and the plasma edge is analysed for the two types of sample.

The IR optical properties of the thermal electrons in silicon

Abstract From precise IR reflection measurements of the thermally agitated Si(111) face with an impurity concentration in the range 5.0×10 16 −7.0× 10 20 cm -3 , it was found that the modulation effects could be classified into three types. In region I the reflection profile remained without modulation due to the thermally insensitive free surface electrons. In region II the reflection profile increased sensitively with thermal agitation for silicon with an impurity concentration N of less than 10 18 cm -3 owing to A-type thermal electrons. In region III the optical behaviour originates from the thermally agitated excess electrons in the range N >#62;10 18 cm -3 . Here, the reflection profile exhibited an increase due to B-type thermal electrons. In the range N >#62;9.0×10 19 cm -3 the reflection profile exhibited a decrease due to C-type thermal electrons.