Flatband voltage

Figure 4. Current-voltage curves of a CdS electrode in 0.2M Na2SOi from Ref. 26. Figure 10 replotted relative to flatband voltage. (1) No Na2S added (2) 5 X 10 M NasS (3) 10 3M Na2S (4) 10 2M Na.2S (5) 10 M Na,S(21).

Now we see that the vacuum levels above the same metal M are not equal. The resulting difference is the flatband voltage Vfb which must be externally applied in order to maintain the flatband condition. Thus, the flatband voltage (multiplied by the test charge) equals the difference in the electron work function of Pd and Si. In the nonideal junctions there are other charges and dipoles in this structure that must be added to the overall Vfb. 

Table V. Comparison of the Barrier Height or Flatband Voltage Change for Different Sensor Structures...

Using the CV flatband voltage shift under bias-temperature stress measurements, the mobile Ion (Na" ") density In the SOG film was determined to be about IXIOH cm . ... 

The ferroelectric hysteresis of P(VDF-TrFE) is directly investigated by MIS capacitors and OFETs. By using MIS capacitors, a systematic shift of flatband voltage is observed, after applieation of different voltage scan windows. The MIS structures are built up as Al/P(VDF-TrFE)/Si02/Si sandwieh strueture. The dependence of the remanent polarisation on thickness of the eopolymer shows an elevated polarisation voltage for a copolymer film thiekness below 100 nm, obviously due to the above mentioned interface reaction between the eopolymer and aluminium. 

The point in the gate voltage sweep at which mobile charges in the channel appear or disappear can be relatively clearly observed this way, and the voltage at which accumulation in the channel begins can be interpreted as the threshold (or flatband) voltage. 

This method has several advantages and disadvantages over the use of I-V curve fitting to determine the flatband voltage ... 

Annie Wang, loannis Kymissis, Vladimir Bulovic, and Akintunde 1. Akin-wande. Tunable threshold voltage and flatband voltage in pentacene field effect transistors. Applied Physics Letters, 89(ll) 112109-3, 2006. 

FET and flatband voltage for an MOS capacitor) and 9 is the fractional coverage of the sites at the interface. 

We now win make the definition of threshold voltage precise and relate its magnitude to the doping profile inside the device, as well as other device parameters such as oxide thickness and flatband voltage. 

Ordinarily interface-trap charge is negligible (< 10 °/cm in silicon MOSFETs) and the other nonideal effects on threshold voltage are accounted for by introducing the flatband voltage Vfb, which corrects the gate bias for these contributions. Then, using Eq. (7.8) with Fox = (Vth — — 4>r t)/d we find... 

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