Resist exposure response curves

Resolution (y) or contrast, has different definitions for positive and negative resists. For positive resists, Yp is a function of both the rate of degradation and the rate of change of solubility of the resist on exposure, whereas for a negative resist, y is a function of the rate of gel formation. Numerical values are obtained from the slope of the linear portion of the response curve and are given by ... 

The proliferation of A549 cells in 72 h following a 30 min exposure to increasing concentrations of BLM is shown in Fig. 1. The dose response curve is biphasic, with apparently sensitive and resistant populations of cells. Cytotoxicity was enhanced by SAAB only at BLM concentrations greater than 20 jug ml", i.e. only in resistant cells. A more detailed study in the range 0-10 jUg BLM ml ( sensitive cells) failed to reveal any potentiation by SAAB (results not shown). 

Figure 22.7 Characterization of the detection properties of a single MOX sensor, (a) Sensor response (sensor resistance) to an exposure to NO2 (0.5 to 2.5 ppm) and CO (6 to 50 ppm). Each gas exposure was maintained for one hour before the ambient gas atmosphere was switched back to carrier gas. NO2 leads to a sensor resistance increase, CO decreases the resistance, (b) Calibration curves for CO and NO2 as derived from (a). The data points represent the sensor resistance values averaged over the last 10 min of gas exposure. The error bars represent the corresponding standard deviations. The calibration curves are used to estimate the LDL for NO2 and CO detection. The partial derivative of each calibration curve is used to determine the sensitivity values (see [d]). (c) Sensor signals S for CO and NO2 and the mean resistance values from (b). (d) Sensitivity m for CO and NO2 as calculated by determining the partial derivative of the calibration curves (b). (e) Analytical sensitivity y as determined for NO2 and CO using the sensitivity values (d) and the standard deviation of the resistance values (b). (f) Accuracy of the CO and NO2 detection as a function of the gas concentration, reproduced from [30] by permissions of Shaker-Verlag...

Fig. 169. Response of the sensing element in the presence of (i) 194 ppm and (ii) 10000 ppm hydrogen in air. A -absorption, B - desorption, (hi) Resistance versus time curve, for a 55 nm Sm him capped with Pd overlayer, on exposure to 10 000 ppm of CO2, H2S, argon plus CH4 and argon plus C2H5OH (Kumar et al., 2002).

The third block in Fig. 2.1 shows the various possible sensing modes. The basic operation mode of a micromachined metal-oxide sensor is the measurement of the resistance or impedance [69] of the sensitive layer at constant temperature. A well-known problem of metal-oxide-based sensors is their lack of selectivity. Additional information on the interaction of analyte and sensitive layer may lead to better gas discrimination. Micromachined sensors exhibit a low thermal time constant, which can be used to advantage by applying temperature-modulation techniques. The gas/oxide interaction characteristics and dynamics are observable in the measured sensor resistance. Various temperature modulation methods have been explored. The first method relies on a train of rectangular temperature pulses at variable temperature step heights [70-72]. This method was further developed to find optimized modulation curves [73]. Sinusoidal temperature modulation also has been applied, and the data were evaluated by Fourier transformation [75]. Another idea included the simultaneous measurement of the resistive and calorimetric microhotplate response by additionally monitoring the change in the heater resistance upon gas exposure [74-76]. 

FIGURE 11-6 Ozone concentration vs. duration of exposure required to produce a S% response in three diffinent plant susceptibility groupings. The curves were generated by developing 95% confidence limits around the equations for all plants in each susceptibility grouping from Table 11-25. Qirves a > sensitive plants, b intermediate ants, c > resistant plants. 

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