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Study of the Ta2O5 insulating layer degradation
Velísek, Martin ; Majzner, Jiří (referee) ; Sedláková, Vlasta (advisor)
The aim of the thesis is to examine the dielectric function Ta2O5 insulating layers in tantalum capacitors. The capacitor plugged in the regular mode represents a MIS structure of reverse direction. Three different factors can be determined for the residual current of the component according to its charge transmission mode: the ohmic, Pool–Frenkel, tunnel and Schottky. An apparatus was constructed by the author of the thesis to measure the temporary connection between residual current and rise of temperature of the tantalum capacitors. Annealing of three different sets of tantalum capacitors made by different producers was performed at the temperature of 400 K and nominal voltage of 35 V during the period of 20 days.The experiment has proved the residual current in the electric field changes with rising temperature in time as a result of the ion movement. The singular factors of the residual current are influenced during the process. By the “ion movement” is meant the ion drift influenced by the attached electric field and diffusion caused by the concentration gradient. First, the samples were being annealed for c. 2 x 106 s, and then the residual current was being regenerated under the voltage of 5 V for 106 s. The residual current values increased considerably after annealing, and decreased again to more or less the original level after the regeneration, some of the samples reaching even values bellow the original level. The VA characteristics of the samples measured before and after the process of controlled obsolescence, and after the regeneration prove not only a change in parameters of the different current factors, but also a change of the current transmission mechanism employed in the process.
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Transport and noise characteristics of MIS structure and their aplication on the NbO capacitors
Velísek, Martin ; Majzner, Jiří (referee) ; Sedláková, Vlasta (advisor)
The aim of my work was the study of niob-oxide capacitor properties. Capacitor structure NbO-Nb2O5-MnO represents the M-I-S structure where NbO anod has metalic conductivity and MnO2 is semiconductor. The capacitor connected in the normal mode with the positive voltage on the NbO anode represents the MIS structure connected in the reverse direction, when the applied votlage increases the potencial barrier between the insulator Nb2O5 and semiconductor (MnO2). The charge carrier transport is the Nb2O5 layer is determined by the Poole-Frenkel mechanism and tuneling in the normal mode. Poole-Frenkel mechanism of the charge carrier transport is dominant for low electric field in the dielectric layer; tunneling current is dominant for the high electric field. We can estimate the effective thickness of the dielectric layer and the ratio between the Poole-Frenkel and tunelling current from the modeling of measured VA characteristics.
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Automated measuring station
Veselý, David ; tk,, Jiří Tlustý ,atx – (referee) ; ATX, Jiří Hronek, (advisor)
This work deals with questions about the measuring of the tantalum capacitor leakage current. This thesis answers to many questions of this sphere e.g. Study of basic parameters, analysis of the measurment LI Head, creating software for the connection between the measuring LI Head, the computer and the analog measuring card, activation of the measuring set, verification of set functionality and economic evaluation of the whole project.
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Transport and noise characteristics of MIS structure and their aplication on the NbO capacitors
Velísek, Martin ; Majzner, Jiří (referee) ; Sedláková, Vlasta (advisor)
The aim of my work was the study of niob-oxide capacitor properties. Capacitor structure NbO-Nb2O5-MnO represents the M-I-S structure where NbO anod has metalic conductivity and MnO2 is semiconductor. The capacitor connected in the normal mode with the positive voltage on the NbO anode represents the MIS structure connected in the reverse direction, when the applied votlage increases the potencial barrier between the insulator Nb2O5 and semiconductor (MnO2). The charge carrier transport is the Nb2O5 layer is determined by the Poole-Frenkel mechanism and tuneling in the normal mode. Poole-Frenkel mechanism of the charge carrier transport is dominant for low electric field in the dielectric layer; tunneling current is dominant for the high electric field. We can estimate the effective thickness of the dielectric layer and the ratio between the Poole-Frenkel and tunelling current from the modeling of measured VA characteristics.
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Study of the Ta2O5 insulating layer degradation
Velísek, Martin ; Majzner, Jiří (referee) ; Sedláková, Vlasta (advisor)
The aim of the thesis is to examine the dielectric function Ta2O5 insulating layers in tantalum capacitors. The capacitor plugged in the regular mode represents a MIS structure of reverse direction. Three different factors can be determined for the residual current of the component according to its charge transmission mode: the ohmic, Pool–Frenkel, tunnel and Schottky. An apparatus was constructed by the author of the thesis to measure the temporary connection between residual current and rise of temperature of the tantalum capacitors. Annealing of three different sets of tantalum capacitors made by different producers was performed at the temperature of 400 K and nominal voltage of 35 V during the period of 20 days.The experiment has proved the residual current in the electric field changes with rising temperature in time as a result of the ion movement. The singular factors of the residual current are influenced during the process. By the “ion movement” is meant the ion drift influenced by the attached electric field and diffusion caused by the concentration gradient. First, the samples were being annealed for c. 2 x 106 s, and then the residual current was being regenerated under the voltage of 5 V for 106 s. The residual current values increased considerably after annealing, and decreased again to more or less the original level after the regeneration, some of the samples reaching even values bellow the original level. The VA characteristics of the samples measured before and after the process of controlled obsolescence, and after the regeneration prove not only a change in parameters of the different current factors, but also a change of the current transmission mechanism employed in the process.
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|
|
Automated measuring station
Veselý, David ; tk,, Jiří Tlustý ,atx – (referee) ; ATX, Jiří Hronek, (advisor)
This work deals with questions about the measuring of the tantalum capacitor leakage current. This thesis answers to many questions of this sphere e.g. Study of basic parameters, analysis of the measurment LI Head, creating software for the connection between the measuring LI Head, the computer and the analog measuring card, activation of the measuring set, verification of set functionality and economic evaluation of the whole project.
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