Spin accumulation created electrically in an n-type germanium channel using Schottky tunnel contacts

Using high-quality Fe$_{3}$Si/$n^{+}$-Ge Schottky-tunnel-barrier contacts, we study spin accumulation in an $n$-type germanium ($n$-Ge) channel. In the three- or two-terminal voltage measurements with low bias current conditions at 50 K, Hanle-effect signals are clearly detected only at a forward-biased contact. These are reliable evidence for electrical detection of the spin accumulation created in the $n$-Ge channel. The estimated spin lifetime in $n$-Ge at 50 K is one order of magnitude shorter than those in $n$-Si reported recently. The magnitude of the spin signals cannot be explained by the commonly used spin diffusion model. We discuss a possible origin of the difference between experimental data and theoretical values.Comment: 4 pages, 3 figures, To appear in J. Appl. Phy

Charge-noise-free Lateral Quantum Dot Devices with Undoped Si/SiGe Wafer

We develop quantum dots in a single layered MOS structure using an undoped Si/SiGe wafer. By applying a positive bias on the surface gates, electrons are accumulated in the Si channel. Clear Coulomb diamond and double dot charge stability diagrams are measured. The temporal fluctuation of the current is traced, to which we apply the Fourier transform analysis. The power spectrum of the noise signal is inversely proportional to the frequency, and is different from the inversely quadratic behavior known for quantum dots made in doped wafers. Our results indicate that the source of charge noise for the doped wafers is related to the 2DEG dopant.Comment: Proceedings of the 12th Asia Pacific Physics Conferenc

On the Fertilization of the Triploid Ginbuna

The ferilization process of the gynogenetic triploid ginbuna Carassius auratus langsdorfii were observed histologically. In the triploid female, it has been reported that the sperm nucleus remains in condensed condition throughout the ferilization to first cleavage. This sperm nucleus does not fuse with female pronucleus, producing the all female triploid offsprings gynogenetically. On the other hand, in the present experiment, in some triploid eggs, the penetrated sperm nucleus swells to form male pronucleus. Some of these eggs develop into tetraploid other than triploid fish. On the scale transplantation experiments between these offsprings, in which all of the sperm nuclei had swollen at the time of fertilization, the unidirectional rejection were observed in two combinations. One of these donors was tetraploid and other was triploid. It seems probable that the former unidirectional rejection might be caused by the introduction of paternal genome, and the later might be caused by the recombination of genes at meiosis or the mutation of the donor and/or the host. From these observation, it was ascertained that the offsprings of triploid ginbuna were not always belonging to the same clone but that some of them differenciated their genome during the gametogenesis or early developmental stage.Article信州大学理学部紀要 19(1): 53-61(1984)departmental bulletin pape

Electrical Detection and Magnetic-Field Control of Spin States in Phosphorus-Doped Silicon

Electron paramagnetic resonance of ensembles of phosphorus donors in silicon has been detected electrically with externally applied magnetic fields lower than 200 G. Because the spin Hamiltonian was dominated by the contact hyperfine term rather than by the Zeeman terms at such low magnetic fields, superposition states $\alpha{}| \uparrow \downarrow >+\beta{}| \downarrow \uparrow >$ and $-\beta{}| \uparrow \downarrow > + \alpha{}| \downarrow \uparrow >$ were formed between phosphorus electron and nuclear spins, and electron paramagnetic resonance transitions between these superposition states and $| \uparrow \uparrow >$ or $| \downarrow \downarrow >$ states are observed clearly. A continuous change of $\alpha{}$ and $\beta{}$ with the magnetic field was observed with a behavior fully consistent with theory of phosphorus donors in silicon.Comment: 6 pages, 5 figure