The Experts below are selected from a list of 22137 Experts worldwide ranked by ideXlab platform
Gerold W. Neudeck - One of the best experts on this subject based on the ideXlab platform.
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an experimental study of the source drain parasitic resistance effects in amorphous silicon thin film transistors
Journal of Applied Physics, 1992Co-Authors: Shengwen Luan, Gerold W. NeudeckAbstract:The effect of source/drain (S/D) parasitic resistance has been experimentally investigated for amorphous silicon (a‐Si:H) thin film transistors (TFTs). In general, the apparent field effect mobility decreases with decreasing Channel length. However, the apparent threshold voltage is relatively constant. This may be attributed to an ohmic parasitic resistance due to the use of ion‐implanted n+ S/D regions. Self‐consistent results were obtained from both TFTs and from independent test structures for the TFT parasitic resistance, contact resistance, and sheet resistance. The results showed that the current spreading under the S/D regions is most critical in determining the magnitude of the total parasitic resistance. In this regard, both the S/D ion implantation and the S/D to gate overlap reduce the total parasitic resistance. Finally, the parasitic resistance is modeled as a gate voltage‐Modulated Channel resistance, under the gate overlap, in series with a constant minimum contact resistance.
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An experimental study of the source/drain parasitic resistance effects in amorphous silicon thin film transistors
Journal of Applied Physics, 1992Co-Authors: Shengwen Luan, Gerold W. NeudeckAbstract:The effect of source/drain (S/D) parasitic resistance has been experimentally investigated for amorphous silicon (a‐Si:H) thin film transistors (TFTs). In general, the apparent field effect mobility decreases with decreasing Channel length. However, the apparent threshold voltage is relatively constant. This may be attributed to an ohmic parasitic resistance due to the use of ion‐implanted n+ S/D regions. Self‐consistent results were obtained from both TFTs and from independent test structures for the TFT parasitic resistance, contact resistance, and sheet resistance. The results showed that the current spreading under the S/D regions is most critical in determining the magnitude of the total parasitic resistance. In this regard, both the S/D ion implantation and the S/D to gate overlap reduce the total parasitic resistance. Finally, the parasitic resistance is modeled as a gate voltage‐Modulated Channel resistance, under the gate overlap, in series with a constant minimum contact resistance.
Shengwen Luan - One of the best experts on this subject based on the ideXlab platform.
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an experimental study of the source drain parasitic resistance effects in amorphous silicon thin film transistors
Journal of Applied Physics, 1992Co-Authors: Shengwen Luan, Gerold W. NeudeckAbstract:The effect of source/drain (S/D) parasitic resistance has been experimentally investigated for amorphous silicon (a‐Si:H) thin film transistors (TFTs). In general, the apparent field effect mobility decreases with decreasing Channel length. However, the apparent threshold voltage is relatively constant. This may be attributed to an ohmic parasitic resistance due to the use of ion‐implanted n+ S/D regions. Self‐consistent results were obtained from both TFTs and from independent test structures for the TFT parasitic resistance, contact resistance, and sheet resistance. The results showed that the current spreading under the S/D regions is most critical in determining the magnitude of the total parasitic resistance. In this regard, both the S/D ion implantation and the S/D to gate overlap reduce the total parasitic resistance. Finally, the parasitic resistance is modeled as a gate voltage‐Modulated Channel resistance, under the gate overlap, in series with a constant minimum contact resistance.
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An experimental study of the source/drain parasitic resistance effects in amorphous silicon thin film transistors
Journal of Applied Physics, 1992Co-Authors: Shengwen Luan, Gerold W. NeudeckAbstract:The effect of source/drain (S/D) parasitic resistance has been experimentally investigated for amorphous silicon (a‐Si:H) thin film transistors (TFTs). In general, the apparent field effect mobility decreases with decreasing Channel length. However, the apparent threshold voltage is relatively constant. This may be attributed to an ohmic parasitic resistance due to the use of ion‐implanted n+ S/D regions. Self‐consistent results were obtained from both TFTs and from independent test structures for the TFT parasitic resistance, contact resistance, and sheet resistance. The results showed that the current spreading under the S/D regions is most critical in determining the magnitude of the total parasitic resistance. In this regard, both the S/D ion implantation and the S/D to gate overlap reduce the total parasitic resistance. Finally, the parasitic resistance is modeled as a gate voltage‐Modulated Channel resistance, under the gate overlap, in series with a constant minimum contact resistance.
Ramon Latorre - One of the best experts on this subject based on the ideXlab platform.
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localization of the k lock in and the ba2 binding sites in a voltage gated calcium Modulated Channel implications for survival of k permeability
The Journal of General Physiology, 1999Co-Authors: Cecilia Vergara, Osvaldo Alvarez, Ramon LatorreAbstract:Using Ba2+ as a probe, we performed a detailed characterization of an external K+ binding site located in the pore of a large conductance Ca2+-activated K+ (BKCa) Channel from skeletal muscle incorporated into planar lipid bilayers. Internal Ba2+ blocks BKCa Channels and decreasing external K+ using a K+ chelator, (+)-18-Crown-6-tetracarboxylic acid, dramatically reduces the duration of the Ba2+-blocked events. Average Ba2+ dwell time changes from 10 s at 10 mM external K+ to 100 ms in the limit of very low [K+]. Using a model where external K+ binds to a site hindering the exit of Ba2+ toward the external side (Neyton, J., and C. Miller. 1988. J. Gen. Physiol. 92:549–568), we calculated a dissociation constant of 2.7 μM for K+ at this lock-in site. We also found that BKCa Channels enter into a long-lasting nonconductive state when the external [K+] is reduced below 4 μM using the crown ether. Channel activity can be recovered by adding K+, Rb+, Cs+, or NH4 + to the external solution. These results suggest that the BKCa Channel stability in solutions of very low [K+] is due to K+ binding to a site having a very high affinity. Occupancy of this site by K+ avoids the Channel conductance collapse and the exit of Ba2+ toward the external side. External tetraethylammonium also reduced the Ba2+ off rate and impeded the Channel from entering into the long-lasting nonconductive state. This effect requires the presence of external K+. It is explained in terms of a model in which the conduction pore contains Ba2+, K+, and tetraethylammonium simultaneously, with the K+ binding site located internal to the tetraethylammonium site. Altogether, these results and the known potassium Channel structure (Doyle, D.A., J.M. Cabral, R.A. Pfuetzner, A. Kuo, J.M. Gulbis, S.L. Cohen, B.T. Chait, and R. MacKinnon. 1998. Science. 280:69–77) imply that the lock-in site and the Ba2+ sites are the external and internal ion sites of the selectivity filter, respectively.
Hung Fat Tse - One of the best experts on this subject based on the ideXlab platform.
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State-Dependent Accessibility of the P-S6 Linker of Pacemaker (HCN) Channels Supports a Dynamic Pore-to-Gate Coupling Model
Journal of Membrane Biology, 2009Co-Authors: Chung Wah Siu, Ezana M. Azene, Chu Pak Lau, Hung Fat TseAbstract:The hyperpolarization-activated cyclic nucleotide-Modulated Channel gene family (HCN1-4) encodes the membrane depolarizing current that underlies pacemaking. Although the topology of HCN resembles K_v Channels, much less is known about their structure-function correlation. Previously, we identified several pore residues in the S5-P linker and P-loop that are externally accessible and/or influence HCN gating, and proposed an evolutionarily conserved pore-to-gate mechanism. Here we sought dynamic evidence by assessing the functional consequences of Cys-scanning substitutions in the unexplored P-S6 linker (residues 352–359), the HCN1-R background (that is, r esistant to sulfhydryl-reactive agents). None of A352C, Q353C, A354C, P355C, V356C, S357C, M358C, or S359C produced functional currents; the loss-of-function of Q353C, A354C, S357C, and M358C could be rescued by the reducing agent dithiothreitol. Q353C, A354C, and S357C, but not M358C and HCN1-R, were sensitive to Cd^2+ blockade (IC_50 = 3–12 μM vs. >1 mM). External application of the positively charged covalent sulfhydryl modifier MTSET irreversibly reduced I _−140mV of Q353C and A354C to 27.9 ± 3.4% and 58.2 ± 13.1% of the control, respectively, and caused significant steady-state activation shifts (∆ V _1/2 = –21.1 ± 1.6 for Q353C and −10.0 ± 2.9 mV for A354C). Interestingly, MTSET reactivity was also state dependent. MTSET, however, affected neither S357C nor M358C, indicating site specificity. Collectively, we have identified novel P-S6 residues whose extracellular accessibility was sterically and state dependent and have provided the first functional evidence consistent with a dynamic HCN pore-to-gate model.
Cecilia Vergara - One of the best experts on this subject based on the ideXlab platform.
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localization of the k lock in and the ba2 binding sites in a voltage gated calcium Modulated Channel implications for survival of k permeability
The Journal of General Physiology, 1999Co-Authors: Cecilia Vergara, Osvaldo Alvarez, Ramon LatorreAbstract:Using Ba2+ as a probe, we performed a detailed characterization of an external K+ binding site located in the pore of a large conductance Ca2+-activated K+ (BKCa) Channel from skeletal muscle incorporated into planar lipid bilayers. Internal Ba2+ blocks BKCa Channels and decreasing external K+ using a K+ chelator, (+)-18-Crown-6-tetracarboxylic acid, dramatically reduces the duration of the Ba2+-blocked events. Average Ba2+ dwell time changes from 10 s at 10 mM external K+ to 100 ms in the limit of very low [K+]. Using a model where external K+ binds to a site hindering the exit of Ba2+ toward the external side (Neyton, J., and C. Miller. 1988. J. Gen. Physiol. 92:549–568), we calculated a dissociation constant of 2.7 μM for K+ at this lock-in site. We also found that BKCa Channels enter into a long-lasting nonconductive state when the external [K+] is reduced below 4 μM using the crown ether. Channel activity can be recovered by adding K+, Rb+, Cs+, or NH4 + to the external solution. These results suggest that the BKCa Channel stability in solutions of very low [K+] is due to K+ binding to a site having a very high affinity. Occupancy of this site by K+ avoids the Channel conductance collapse and the exit of Ba2+ toward the external side. External tetraethylammonium also reduced the Ba2+ off rate and impeded the Channel from entering into the long-lasting nonconductive state. This effect requires the presence of external K+. It is explained in terms of a model in which the conduction pore contains Ba2+, K+, and tetraethylammonium simultaneously, with the K+ binding site located internal to the tetraethylammonium site. Altogether, these results and the known potassium Channel structure (Doyle, D.A., J.M. Cabral, R.A. Pfuetzner, A. Kuo, J.M. Gulbis, S.L. Cohen, B.T. Chait, and R. MacKinnon. 1998. Science. 280:69–77) imply that the lock-in site and the Ba2+ sites are the external and internal ion sites of the selectivity filter, respectively.