Amorphous thin GeSbTe phase-change films prepared by radical-assisted metal-organic chemical vapor deposition

AbstractAmorphous thin Ge2Sb2Te5 films were deposited by MOCVD (metal organic chemical vapor deposition) on three-dimensional structures. Ammonium gas, used as a reactant, reduced the deposition temperature to 150°C, which is lower than that of metal-organic precursors. Introducing nitrogen and hydrogen radicals made by decomposition of the ammonium gas further reduced the growth temperature. The lowest growth temperature producing a realistic growth rate was 100°C. Phase-change memory cells made of MOCVD-grown films were confirmed to have operation and reliability characteristics as good as those of conventional cells made of sputter-deposited films

Spin fluctuations in CuGeO3_3 probed by light scattering

We have measured temperature dependence of low-frequency Raman spectra in CuGeO$_3$, and have observed the quasi-elastic scattering in the $(c,c)$ polarization above the spin-Peierls transition temperature. We attribute it to the fluctuations of energy density in the spin system. The magnetic specific heat and an inverse of the magnetic correlation length can be derived from the quasi-elastic scattering. The inverse of the magnetic correlation length is proportional to $(T-T_{SP})^{1/2}$ at high temperatures. We compare the specific heat with a competing-$J$ model. This model cannot explain quantitatively both the specific heat and the magnetic susceptibility with the same parameters. The origin of this discrepancy is discussed.Comment: 17 pages, REVTeX, 5 Postscript figures; in press in PR

Dataset for Single Carrier Trapping and Detrapping in Scaled Silicon Complementary Metal-Oxide-Semiconductor Field-Effect Transistors at Low Temperatures

Dataset supporting: Li, Zuo et al (2017) Single Carrier Trapping and Detrapping in Scaled Silicon Complementary Metal-Oxide-Semiconductor Field-Effect Transistors at Low Temperatures. IOP nanotechnology.</span

Single carrier trapping and de-trapping in scaled silicon complementary metal-oxide-semiconductor field-effect transistors at low temperatures

The scaling of Silicon (Si) technology is approaching the physical limit, where various quantum effects such as direct tunnelling and quantum confinement are observed, even at room temperatures. We have measured standard Complementary Metal-Oxide-Semiconductor Field-Effect-Transistors (CMOSFETs) with wide and short channels at low temperatures to observe single electron/hole characteristics due to local structural disturbances such as roughness and defects. In fact, we observed Coulomb blockades in sub-threshold regimes of both {\it p}-type and {\it n}-type Si CMOSFETs, showing the presence of quantum dots in the channels. The stability diagrams for the Coulomb blockade were explained by the potential minima due to poly-Si grains. We have also observed sharp current peaks at narrow bias windows at the edges of the Coulomb diamonds, showing resonant tunnelling of single carriers through charge traps

Quantum dipole in a silicon transistor: Quantum simulation for strongly correlated system

We discovered anomalous transport properties in a conventional Si based Metal-Oxide-Semiconductor Field-Effect-Transistor with a wide and narrow hole-channel at low temperatures. We found the quantum dipole formed at the thin gate interface is responsible for the phase transition. We discuss its potential to use for a quantum simulator as a test bed to examine various theoretical concepts in condensed-matter physics

Random telegraph noise from resonant tunnelling at low temperatures

The Random Telegraph Noise (RTN) in an advanced Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) is consideredto be triggered by just one electron or one hole, and its importance is recognised upon the aggressive scaling. However, the detailed nature of the charge trap remains to be investigated due to the difficulty to find out the exact device, which shows the RTN feature over statistical variations. Here, we show the RTN can be observed from virtually all devices at low temperatures, and provide a methodology to enable a systematic way to identify the bias conditions to observe the RTN. We found that theRTN was observed at the verge of the Coulomb blockade in the stability diagram of a parasitic Single-Hole-Transistor (SHT), and we have successfully identified the locations of the charge traps by measuring the bias dependence of the RTN

Quantum dipole effects in a silicon transistor under high electric fields

Low dimensional strongly correlated electron systems exhibit a variety of exotic phenomena such as fractional quantum Hall effects, high-temperature superconductivity, and topological phase transitions. However, a problem in modern condensed-matter physics is the difficulty to compare theories with experiments, because of the absence of an ideal experimental system whose properties can be controlled in a systematic way. Here we show a state-of-the-art silicon technology can provide a platform to investigate a one-dimensional quantum system, where various theoretical predictions are available on the basis of mathematically rigid models. We have found unusual transport properties in a field-effect-transistor with a wide and short hole-channel under strong electric fields at low temperatures. By gate-induced doping in the transistor, we discovered new current plateaus and negative differential conductances against drain voltages. We have also found anomalous gate leakage currents which increases upon reducing temperatures and reducing the external electric fields. This provides evidence of the broken symmetry of quantum dipoles formed at the gate interface, which increases local electric fields coming from molecular mean-fields. We obtained phase diagrams of the field-induced phase transitions, which will be correlated with a one-dimensional quantum dipole model

Dataset for Quantum Dipole Effects in a Silicon Transistor under High Electric Fields

Saito, S., Li, Z., Yoshimoto, H., Tomita, I., Tsuchiya, Y., Sasago, Y., ... Kurihara, S. (2018). Quantum dipole effects in a silicon transistor under high electric fields. Journal of the Physical Society of Japan. DOI: 10.7566/JPSJ.87.094801</span