Reversible Bias Stress

Kinetic modeling was used to estimate the depth of the fast, reversible traps in PQT-12. We assume that the square law observed during trapping is indicative of a trap state made of two correlated holes (i.e. a bipolaron, see Section 5.3.4). Making use of detailed balance we obtain  

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The recovery rate of the reversible traps determines the duty-cycle cut-off below which only long-lived traps contribute to bias stress. At higher duty cycle, the current decay is the result of the simultaneous interplay of fast and slow trapping. 

A. Salleo, R. A. Street, Light-induced bias stress reversal in polyfluorene fhin-film transistors, ... 

Generally, bias-stress instability refers to long-term changes in the transistor characteristics that do not saturate but continue without limit until the device is rendered useless. Hysteresis refers to short-term reversible shifts in the characteristics that lead to looping in the measured characteristics, depending on the direction in which the bias voltages are swept. There is no sharp distinction between bias-stress instability and hysteresis, and the two may arise from the same or similar physical causes. 

G. Gu, personal communication. On the other hand, it has been reported that illumination can assist in recovery from bias-stress effects in polymer TFTs. See Salleo, A. and Street, R.A., Light-induced bias stress reversal in polyfluorene thin-film transistors, J. Appl. Phys., 94, 471 2003. 

In addition to reversible hysteretic effects, irreversible storage, photoin-duced, and bias-stress can also be observed in many OFET systems. Repeated characterization through the application of the stressor will expose these effects. 

Fukuda K, Suzuki T, Kumaki D, Tokito S. Reverse DC bias stress shifts in orgaific thin-film transistors with gate dielectrics using parylene-c. Phys Status Solidi A 2012 209(10) 2073-7. 

By definition, plasma is an ionized gas that is spacially neutral. That is, there are an approximately equal munber of positive and negative charges in a given volume. It should also be stressed that these are radio-frequency plasmas, not direct current plasmas. The terms anode and cathode have no meaning, on the time scale of diffusion, because the polarity of the electrodes is reversing every 37 nsec (at 13.56 MHz). Because there is only a few V/cm gradient in the plasma, and because of the enormous mass difference between electrons and ions, the motion of the ions is almost unaffected by the RF field. However, ions may be affected by the build-up of a DC self-bias on the electrodes if the electrodes are of different areas. 

Bias-induced reverse piezoelectric response Broadband dielectric spectroscopy (BDS) Dielectric permittivity spectrum Dielectric resonance spectroscopy Elastic modulus Ferroelectrets Electrical breakdown Acoustic method Characterization Dynamic coefficient Interferometric method Pressure and frequency dependence of piezoelectric coefficient Profilometer Quasistatic piezoelectric coefficient Stress-strain curves Thermal stability of piezoelectricity Ferroelectric hysteresis Impedance spectroscopy Laser-induced pressure pulse Layer-structure model of ferroelectret Low-field dielectric spectroscopy Nonlinear dielectric spectroscopy Piezoelectrically generated pressure step technique (PPS) Pyroelectric current spectrum Pyroelectric microscopy Pyroelectricity Quasistatic method Scale transform method Scanning pyroelectric microscopy (SPEM) Thermal step teehnique Thermal wave technique Thermal-pulse method Weibull distribution... 

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