. The Bell System technical journal . nd lower lines (by reading gain settings). During a surface photo-voltage measurement, the gold electrode wasdisconnected from the high-voltage supply, and connected to a high-impedance detector, similar to that used in the work of Brattain andBardeen.^ A value for the chopped light intensity was chosen to give acontact potential change that was generally not more than 5 mV. Asimultaneous measurement of the photoconductivity was also made. The gas cycle was similar to that described by Brattain and Bar-deen.^ Some variations were made in it to try to sprea
. The Bell System technical journal . nd lower lines (by reading gain settings). During a surface photo-voltage measurement, the gold electrode wasdisconnected from the high-voltage supply, and connected to a high-impedance detector, similar to that used in the work of Brattain andBardeen.^ A value for the chopped light intensity was chosen to give acontact potential change that was generally not more than 5 mV. Asimultaneous measurement of the photoconductivity was also made. The gas cycle was similar to that described by Brattain and Bar-deen.^ Some variations were made in it to try to spread out the rate ofchange with time so that the data could be obtained without large cycle used was: (i) sparked oxygen 1 min, (ii) dry O2, (iii) mixtureof dry and wet O2, (iv) wet O2, (v) wet No, (vi) a mixture of dry andwet N2, (vii) dry O2, (viii) dry O2, triple flow, and (ix) ozone normalflow. The normal rate of gas flow was about 2 liters per minute; the wetgas was obtained by bubbling through water (probably about 90 per. Fig. 3 — Picture of field effect-photoconductivity pattern, as observed onoscilloscope. Dark curve at the bottom. , COMBINED MEASUREMENTS ON ETCHED GERMANIUM SURFACES 1027 cent ) and the mixture of dry and wet was obtained by letting ap-proximately one-half the gas flow bubble through H2O. In carrying outthe experiment, it was found convenient to carry out alternately a com-plete cycle of field effect and surface photo-voltage measurements. Thevalues of the photoconductivity at equivalent points in successive cyclescould be compared, in order to check that no systematic error was intro-duced by this procedure. In addition to the foregoing, the folloAving measurements Avere made: 1. All dimensions were determined. 2. The resistivity of the sample was found, and also the body life-time, on another specimen cut from the same crystal. 3. The amplitude of the voltage swing was measured. 4. The amplifiers in the field effect circuit were calibrate
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