Hot́ hole anisotropic effect in silicon and germanium

Anisotropic effect of the hole drift velocity in silicon and germanium has been investigated with the time of flight technique by applying the electric field parallel to the <100 and <111 crystallographic axis. The measurements were performed for electric fields ranging from 10 to 3 × 10⁴V/cm and temperatures from 40 to 200°K. The results indicate that the anisotropic effect v_d<100/v_d<111 increases with decreasing temperature and increasing electric field, and reaches a saturation value at high electric fields (? 10⁴V/cm). The maximum anisotropic effect for Ge is 1.25 at 40°K and for Si is 1.2 at 45°K. A qualitative analysis of the experimental data indicates that the anisotropic effect is due to the warped heavy-valence-band shape.     

Hodge theory used to produce finite self-energy models of the electron

The relationship between electromagnetic fields and topology is discussed. Hodge theory is generalized to classify static fields in static wormhole models. This generalization is used to show models of the electron exist which have finite self-energy. These models always have 1/R ² electric fields and self-energies of 4πq ²/R ₀, whereR ₀ is the inner radius of the wormhole.     

Level-crossing-Experiment zur Untersuchung des Einflusses eines elektrischen Feldes auf die Hyperfeinstruktur des 4p 2 P 3/2-Terms im Cu I-Spektrum

Level-crossing technique applying parallel electric and magnetic fields has been used to investigate the influence of an electric fieldE _z on the hyperfine structure of the 4p ² P _3/2-state. The Stark shift of the level-crossing nearH _z =155 Oe and the modification of the magnetic zero-field level-crossing signal due to the electric fieldE _z was observed. Both experimental results can be explained with a Stark-constantβ=7.2(1.1)kc(kV/cm)^?2.     

Defect-induced electric fields in ZnS

The optical absorption edge in cubic ZnS shows both phonon- and impurity-induced effects which determine its precise shape. Applying external electric fields and measuring the shift of the absorption edge makes it also possible to compute the impurity excitonic mass which was found to be ? 0.02m₀. Comparing the edge shifts due to the impurity-induced electric fields with those due to the external fields, one finds the approximate value for the average impurity-induced field as being about 3 × 10⁴ V/cm.     

Hall mobility of hot electrons in CdS

Photo-Hall effect of hot electrons in a pure single crystal of CdS was observed, for the first time. The measurement was carried out for electric fields up to 4,300 V/cm in magnetic fields up to 40 kOe at 4.2 K. The saturation of the drift velocity V_d of electrons due to optical phonon emission was observed. The saturated value of V_d is found to be about 1.7 × 10⁷ cm/sec.     

Die Abhängigkeit innerer und äußerer Wechselwirkungen des TlF-Moleküls von der Schwingung,Rotation und Isotopie

The hyperfinestructure, Stark effekt and Zeeman effect of the TlF molecule have been measured with a molecular beam resonance apparatus. The apparatus uses electric four poles as deflecting fields and a homogeneous electric field parallel to a super-imposed magnetic field in the transition region. Electric dipole transitions withΔm _J =±1,ΔJ=0 (J rotational quantum number) were measured in the following (v, J) states (v vibrational quantum number): (0,1), (1,1), (2,1) and (0,2) of the molecule²⁰⁵Tl¹⁹F and (0,1) of the molecule²⁰³Tl¹⁹F. For these five states the following interaction constants were determined: The magnetic (and the electric) dipolemoment of the molecule, the scalar and the tensor nuclear dipole-dipole interaction, the nuclear spin-rotational interactions, the anisotropy of the diamagnetic susceptibility ξ_⊥?ξ_∥, the anisotropy of the diamagnetic shielding of the external field by the electrons at the position of the nuclei σ_⊥?σ_∥. From these quantities it was possible to calculate the quadrupole-moment of the electronic charge distribution. Furthermore, the dependence of the ratio of the isotopic electric dipolemoments on vibrational state was measured. A new method for determining the nuclear magnetic moments is described. The method consists of a molecular beam resonance apparatus with combined magnetic and electric transition fields and was used to measure the magnetic moments of the nuclei²⁰⁵Tl and¹⁹F. — On page 293 will be found a table of results.     

Exchange and hyperfine fields acting on dilute Eu In SmCo5, Sm2(Co1-xFex)17 and Sm2CoxMy( rm M = Fe, Cu, Zn, Zr)

Mössbauer source experiments of dilute ¹⁵³Eu and ⁵⁷Fe in SmCo₅ and ¹⁵³Eu in Sm₂(Co_1-xFe_x)₁₇ and Sm₂ Co_x M_y at 4.1 K were performed. After the ${}^{153}\text{Sm}\text{→β?}{}^{153}$ decay the Eu ion is trivalent and exhibits extremely large hyperfine interactions due to strong exchange fields. Since the exchange interactions are comparable to the Eu³⁺ spin-orbit coupling, we calculated the expectation values of the Eu³⁺ spin, magnetic hyperfine field and electric field gradient as a function of exchange field and second order crystalline field, by diagonalization of the full Hamiltonian of spin orbit, exchange and crystalline field. For SmCo₅ and Sm₂(Co_1-xFe_x)₁₇ the exchange and crystalline fields are known and thus allow us to analyze our experimental results and obtain the polarized conduction electron contributions to the magnetic hyperfine field. The contribution due to magnetic neighbour polarization of conduction electrons is found to be linear in exchange field. The experimental results together with the theoretical analysis yield the Eu electric field gradient 4f Sternheimer shielding factor R_Q to be 0.26±04. It is shown that Mössbauer studies of two probes (¹⁵⁵Gd and Eu³⁺) in magnetic systems yield directly the second order crystalline field, the exchange field and the various contributions to the hyperfine field acting on the Eu nucleus. From the experimentally measured magnetic hyperfine fields alone, approximate values for the exchange fields in the mixed systems Sm₂Co_xM_y were determined.     

Photoelectron injection at metal-semiconductor interfaces

A modelling of the photoinjection process is developed which permits fitting of the spectral photoresponse of Schottky barriers including the electric field dependence of barrier height and photoresponse by means of two adjustable parameters: the zero field barrier qφ_BO and λ₀ the zero temperature mean free path for optical phonon scattering of high energy electrons. The model assumes an image force potential barrier with Thomas-Fermi screening in the metal. Effects of optical phonon scattering and quantum mechanical transmission are convoluted on the Fowler photoelectron supply function. The effects of phonon scattering are frequently large because the ranges in energies associated with the transverse momentum and normal momentum are approximately the amount by which the quantum energy hv exceeds the barrier energy qφ_B. At high fields, quantum mechanical tunneling dominates the response when hv < qφ_B. At low fields, phonon assisted transmission is appreciable for the same quantum energy range. The calculation of the collection probability includes effects of multiple scattering even for electrons that do not lie initially within the cone of acceptance at the barrier maximum. An approach that considers the probability of collection the same as that of reaching the potential maximum without scattering is found to be acceptable only at high fields. Experimental results are reported from oxide-passivated epitaxial Pt_xSi-〈111〉 n-type Si Schottky barrier diodes with annular Schottky barrier guard rings measured at temperatures of 90 and 298 K for an electric field range from 5 × 10³ to 9 × 10⁴$\text{V}\text{cm}$. The field, spectral and temperature dependences of the photoresponse data are in excellent agreement with theoretical predictions with λ₀ = 110 Å at both 90 and 298 K. The zero field barrier height obtained from fitting photoresponse curves at a number of electric fields is also in excellent agreement with I-V and C-V measurements.     

Near stabilization of the Ce moment upon dilution in (Ce,La)Al3

Susceptibility measurements taken for 1.5 ≤ T ≤ 17 K on the system Ce_xLa_1?xAl₃ indicate that the Ce moment is nearly stabilized on dilution. Evidence for this is the fact that the fractional occupancy of the 4f¹ configuration and the spin correlation time both increase as x → 0. Crystalline electric fields influence the susceptibility of these valence fluctuation systems.     

Doppelresonanzuntersuchung des Einflusses eines elektrischen Feldes auf die Zeeman-Aufspaltung des 5s 5p 3P1-Terms im SrI-Spektrum

Under the simultaneous action of external electric and magnetic fields the 5s 5p ³ P ₁-level of the even Sr-isotopes splits into three non-equidistant Zeeman-sublevels. In an atomic beam experiment the spacings between the sublevels were investigated by the double resonance method at a magnetic field strength of ca. 22 Oe and at electric field strengths up to ca. 17 kV/cm. From the r.f.-resonance signals the tensor polarizability of the 5s 5p ³ P ₁-level was deduced to be α_ten(³ P ₁)=6.1(8) kHz/(kV/cm)². This value may be used to get an estimate of the oscillator strength of the infrared transitions between the multiplets 5s 5p ³P and 5s 4d ³ D. Taking into account oscillator strengths of electric dipole transitions to other low lying levels one obtainsf(³ P→³ D)≈0.09.     

Stark-Effekt-Untersuchungen an Strontium durch Nachweis von Δμ=1-level-crossing-Signalen mit linearpolarisiertem Licht

Zero field-level crossing signals of the 5s 5p ¹ P ₁-level of the Sr I-spectrum were investigated in superimposed homogeneous magnetic and electric fields. The electric field-dependent Δμ=1-crossings were detected by resonance scattering of linearly polarized light of the 4607 Å-line, the directions of polarization forming an oblique angle with the field axisz. The experiments yielded the tensor polarizability of the 5s 5p ¹ P ₁-level ¦α_ten¦=15.7 kHz/(kV/cm)². This value is related to oscillator strengths of electric dipole transitions from the 5s 5p ¹ P ₁-level to¹ S ₀- and¹ D ₂-levels. The level crossing signals, obtained by resonance scattering oflinearly polarized light, are discussed using a formula, originally derived by Rose and Carovillano for level crossing experiments withunpolarized light beams. The applicability of the formula to our experiments results from an equivalence of level crossing measurements with unpolarized and those with linearly polarized light beams.     

Effective dielectric theory from QCD

New effective fields are defined in QCD by averaging the phase factor P exp∫_x0^x₀+?iA_μdx^μ in small four-dimensional boxes. Their effective lagrangian is constructed explicitly for G=SU(2). It is a version of the dielectric theory proposed by 't Hooft, Kogut and Susskind. The classical electric flux-tube solution is analyzed quantitatively.     

Stark effect investigations of the 4f 14 6s 6p 3 P 1 and1 P 1 levels of ytterbium

The tensor polarizabilities of the 4f ¹⁴ 6s 6p ³ P ₁ level were investigated for all stable Ytterbium isotopes by the method of optical double resonance. The tensor polarizabilities were deduced from the rf-resonance signals in parallel electric and magnetic fields. The value obtained for the even Yb isotopes is in good agreement with the results derived from the measurements on the odd isotopes. The mean value isα _ten(³ P ₁)0=5.99(34)kHz/(kV/cm)². The tensor polarizability of the 4f ¹⁴ 6s 6p ¹ P ₁ level of¹⁷¹Yb was measured by means of the level crossing technique with parallel electric and magnetic fields. The experimental result isα _ten(¹ P ₁)=?14.3(1.4)kHz/(kV/cm)². This is compared with the prediction of the LS coupling approximation using the experimental data of the³ P ₁ level. Only poor agreement is obtained which is due to the configuration mixing in the¹P₁ level.     

Excited quark-quark interactions in a bag model

We calculate the colour magnetic and electric fields,B ^a andE ^a , in the static cavity approximation of the MIT bag model. This is done rigorously for all direct and exchange four-currents of quarks in theS _1/2,P _1/2 andP _3/2 bag states. We then find the quark-quark colour interaction for direct and exchange diagrams. The one-pion exchange diagrams due to chiral symmetry are also calculated.     

Electrical properties of highly (111)-oriented lead zirconate thin films

Antiferroelectric PbZrO₃ thin films were grown on Pt/Ti/SiO₂/Si substrates with predominant (111) orientation using a sol-gel process. The Pt/PbZrO₃/Pt film capacitor showed well-saturated hysteresis loops at an applied voltage of 5 V with remanent polarisation (P_r) and coercive electric field (E_c) values of 8.97 μC/cm² and 162 kV/cm, respectively. The leakage current density of the highly (111)-oriented PbZrO₃ film was less than 1.0×10⁻⁷ A/cm² over electric field ranges from 0 to 105 kV/cm. The conduction current depended on the voltage polarity. The PbZrO₃/Pt interface forms a Schottky barrier at electric fields from 20 to 160 kV/cm. The dielectric relaxation current behaviour of Pt/PbZrO₃/Pt capacitor obeys the well-known Curie-Von Schweidler law at electric field of 20-80 kV/cm, the currents have contributions of both dielectric relaxation current and leakage current.     

Low temperature heat capacity and magnetic excitation of HoAl2 in a magnetic field

The specific heat of single crystalline HoAl₂ in magnetic fields up to 7.5 T has been measured for the temperature range 1.5–16 K. In addition the energy of a magnetic excitation in a magnetic field of 5 T at 4.2 K has been determined by inelastic neutron scattering. The results have been interpreted with a cubic crystalline electric field and an exchange interaction using the same parameter set B₄=-0.85×10^-4 meV, B₆=+0.71× 10^-6 meV and T_C=31.5 K previously obtained by magnetization measurements.     

Effect of electric fields on the dynamics of silicon microhardness changes induced by low-intensity β irradiation

Decelerating effect of electric fields on silicon microhardness changes induced by low-intensity (I = 10.4 × 10⁴ cm^?2 s^?1) β irradiation has been revealed. The threshold character of the electric field effect is found (the effect is absent at electric fields E < 350 V cm^?1).     

Level crossing investigations in the 4d 2 D 5/2,3/2-states of the A1 I-spectrum

The level crossing technique with combined electric and magnetic fields was used to investigate the hyperfine structure, the Stark effect, and the mean life time of the 4d ² D _5/2,3/2-states in the Al I-spectrum. The experimental values are discussed in connection with interconfiguration mixing.     

Proton-irradiated Pb(Zr0.52Ti0.48)O3 thick films for flexible non-volatile memory applications

We investigated the ferroelectricity in proton-irradiated flexible Pb(Zr_0.52Ti_0.48)O₃ (PZT) thick films and their non-volatile memory characteristics. The Ni-Cr metal foil substrate allowed high-quality polycrystalline PZT films with flexible functionality to be fabricated using conventional sol-gel and high-temperature annealing methods. The 10-MeV proton-irradiated PZT film exhibited an almost square polarization?electric field hysteresis curve with saturated (P_s) and remnant (P_r) polarizations of 18.9 and 17.0 μC/cm², respectively; which are slightly lower than as-grown PZT with P_s = 28.7 μC/cm² and P_r = 24.3 μC/cm². The P_r did not decrease even after 1000 cycles of continuous bending and unbending at a bending radius of 2.14 mm and decreased slightly to ～80% of its initial value after 10⁵ s. Although the P_r decreased to ～55% after 10¹⁰ cycles, the electric polarization remained switchable under positive and negative electric fields. These characteristics suggest that the flexible PZT films could be utilized in non-volatile memory device applications in environments with high doses of proton irradiation, such as those in aeronautics and nuclear power plants.     

Upper critical fields of superconducting Gd and Tm doped LaSn3: Effects of crystalline electric fields

The temperature dependence of the upper critical fields, H_c²(T), are presented for (La_1-xGd_x)Sn₃ and (La_1-xTm_x)Sn₃. For samples with nearly the same T_c, H_c²(T) of the Tm-doped LaSn₃ samples are always larger than those for the Gd-doped samples. The results are interpreted in terms of crystalline electric field splitting of magnetic levels of the Tm³⁺. Pure LaSn₃ is found to be a Type I superconductor.