摘要:

Cold cathode electron field emission from aragoniteCaCO3whiskers coated with 10-nm-thick gold has been observed. The microstructure of the whiskers grown on a Ni substrate by electrochemical deposition has been examined by scanning electron microscope, energy dispersive x-ray spectrometer, x-ray diffraction spectrometer, and Raman spectroscopy. For a 220 &mgr;m anode-cathode gap, emission current densities in excess of∼2×10−6 A/cm2are observed for applied voltages of 660 V or greater. Although it is believed that the electric field is locally enhanced by the geometry of the whiskers, the voltage required increases roughly linearly with the anode-cathode spacing, corresponding to a turn-on field of approximately 3 V/&mgr;m, and an emission current density of0.4 mA/cm2has been obtained for an applied field of 5.5 V/&mgr;m. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365714

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Diamond films were successfully synthesized in both parallel-plate radio frequency (rf: 13.56 MHz)CH4andCH3OHplasmas with injection of H and OH radicals generated in the remote microwave (2.45 GHz)H2/H2Oplasma. Effects of H, OH, andCH3radicals on the diamond film formation in the rf plasma reactor were investigated by the formation of diamond films employing radical injection technique and the measurement of density in the plasma. Under the condition of diamond film formation,CH3density was measured by infrared diode laser absorption spectroscopy (IRLAS). The kinetics ofCH3in rfCH4andCH3OHplasmas with injection of H and OH radicals were evaluated from the results of optical emission spectroscopy and lifetime ofCH3radicals estimated by IRLAS. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365715

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The influence of imposing an electrical field parallel to the substrate of a growing metallic film was studied experimentally and analyzed theoretically. Ti films were deposited onto glass substrates using a filtered vacuum arc source while a voltageUof 0–300 V was applied between electrodes spaced 16 mm apart on the substrate surface. The current through the film was monitored during the deposition. Several characteristic stages of current evolution were observed after arc initiation: (1) an initial sharp jump of the current, (2) a stage of constant, relatively low current, (3) rapid current growth, (4) slower current growth, and (5) linear growth. Analyses showed that stages (1) and (2) are connected with current conduction through the plasma rather that through the sample while stages (3) and (4) are connected with tunneling and percolation during film formation. The tunneling stage could be distinguished only forU⩽6 V;in other cases, conduction through the plasma obscured the observation. The percolative exponent increased from 1.0 to 2.68 and the critical thickness decreased by a factor of 4.3 with an increasedUfrom 1 to 60 V. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365716

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The Shockley’s diode equation predicts a current-voltage characteristic different from that used by Shockley and Queisser to compute the limiting efficiency of photovoltaic energy conversion under the assumptions of the detailed balance theory. The reasons for such discrepancy are discussed being the neglect of photon recycling effects in Shockley’s diode equation the main cause. This interpretation is crucial to understand the fundamentals on which the computation of the limiting efficiency of solar cells is based. Without photon recycling effects, it can be concluded that the limiting efficiency (one sun) of a gallium arsenide solar cell is 26.8&percent; (with the sun assumed as blackbody at 6000 K) while the true figure is 30.7&percent;, 38.7&percent; as long as the angle of emission of photons from the cell is fully restricted. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365717

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A two-step channelIn0.1Ga0.9As/In0.25Ga0.75Asheterostructure real-space transfer transistor grown by low-pressure metalorgonic chemical vapor deposition is implemented. By virtue of &dgr; doping, shallow ohmic contacts and two-step channel, a high peak-to-valley current ratio up to 260 000 at 300 K can be obtained at low collector voltage(Vc=3 V).Moreover, from Shubnikov–de Haas (SdH) measurements, we observe a positive persistent-photoconductivity effect and variations of quantum lifetime. The SdH result is in good agreement with the critical drained-to-source onset voltage of negative differential resistance. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365718

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have studied the effect of Cl incorporation on the performance of amorphous silicon thin film transistors (a-Si:H(:Cl) TFTs). The off-state leakage current of a-Si:H(:Cl) TFTs under light illumination is much lower than that of a-Si:H TFTs, because the photoconductivity of a-Si:H(:Cl) is much lower than that of conventional a-Si:H. The a-Si:H(:Cl) films deposited between [SiH2Cl2]/[SiH4]=0.04 and[SiH2Cl2]/[SiH4]=0.12show p-type conduction, leading to the much lower photoconductivity. The TFT using a-Si:H(:Cl) deposited with [SiH2Cl2]/[SiH4]=0.04 exhibits a field effect mobility of 0.41 cm2/V s and a threshold voltage of 5.56 V; however the off-state leakage current under light illumination is two orders of magnitude smaller than that of a conventional a-Si:H TFT. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366260

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The influence of film thickness and incident excimer laser energy density on the properties of poly-Si thin film transistors has been investigated and a coherent pattern of behavior has been identified which establishes controlled melt-through of the film as a key condition for achieving high quality devices. The conditions were correlated with the appearance of large grains and gave consistent results from bothn- andp-channel devices, with carrier mobilities of more than 150 and80 cm2/V s,respectively, and leakage currents of less than2×10−14 A/&mgr;m.From a study of static irradiations, using a semi-Gaussian laser beam, the results are shown to be consistent with the super lateral grain growth (SLG) model. The trailing edge of the beam, when used in a swept mode, has been demonstrated to play an important role in extending the size of the energy window for this effect by re-setting the material into the SLG regime. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365719

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The off-state current inn- andp-channel polycrystalline silicon thin-film transistors (polysilicon TFTs) is investigated systematically by conduction measurements at various temperatures and low-frequency noise measurements at room temperature. It is demonstrated that the leakage current is controlled by the reverse biased drain junction. The main conduction mechanisms are due to thermal generation at low electric fields and Poole–Frenkel accompanied by thermionic filed emission at high electric fields. The leakage current is correlated with the traps present in the polysilicon bulk and at the gate oxide/polysilicon interface which are estimated from the on-state current activation energy data. Analysis of the leakage current noise spectral density confirms that deep levels with uniform energy distribution in the silicon band gap are the main factors in determining the leakage current. The density of deep levels determined from noise analysis is in agreement with the value obtained from conductance activation energy analysis. The substantially lower leakage current observed in then-channel polysilicon TFT is explained by the development of positive fixed charges at the interface near the drain junction which suppress the electric field. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365720

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Radiation-induced trapped charge annealing processes in the gate and field oxides of metal–oxide–semiconductor field-effect transistors are thermally activated. The activation energy and the frequency factor are related to the relaxation time constant by an Arrhenius law. A simple measurement of the relaxation time constant defines the activation energy, frequency factor(E,&ngr;)pair. Choosing arbitrarily a “realistic” frequency factor corresponds to determining a characteristic energy, on which depends any subsequent annealing prediction. A controversy exists about the appropriate value of &ngr; for silicon dioxide, with published values ranging from1×107to1×1014 s−1.In this paper, a new method is presented that yields values for both frequency factor and activation energy. This method leads to an unexpectedly low (but consistent) value of &ngr; (about1×107 s−1) when applied to three different devices, obtained from three different manufacturers. The experimental procedure and the results for all three cases are presented and discussed. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365721

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Fowler–Nordheim (FN) tunneling electron injection was performed in Al/Si oxynitride/Si capacitors and compared with the results for the thermal Si oxides grown at 850 and 900 °C as well as the plasma oxide. The Si oxynitride was grown by direct oxynitridation of the Si substrate using helicon-wave excited nitrogen–argon mixed plasma around room temperature. The shift of the threshold voltageVth[the inversion voltage of capacitance–voltage(C–V)curves] was much larger for the negative stress than for the positive stress, similar to the case ofSiO2.TheVthshifts were much smaller for the plasma-grown Si oxynitride than for the thermal and plasmaSiO2when the oxynitride sample was annealed at moderate temperatures (300–500 °C) in nitrogen ambient. These findings can be explained on the basis of surface plasmon and avalanche breakdown models proposed as the explanation of hot-carrier injection instability inSiO2.When the Si oxynitride samples were annealed at high temperature (800 °C), anomalousC–curves were observed and the degradation was very great, especially for positive bias FN stress. These results are also tentatively explained. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365722

出版商:AIP    

年代:1997

数据来源: AIP