790 



THE BELL SYSTEM TECHNICAL JOURNAL, JULY 195G 



Table V 



treatments in H2O2 (superoxol strength). In general, no great differences 

 were observed in the unformed alpha and /c(0, — 10) after the treatment. 

 However, in isolated cases, unformed units made on etched p-gerraanium 

 treated in this way exhibit output characteristic anomalies of the type 

 characterized by Miller as type (1). It was later found that the same 

 surface treatment can produce a similar result on etched 11-germanium 

 surfaces, again only in isolated locations on the surface. An output char- 

 acteristic of this form is shown in Fig. 11. This unformed unit was made 

 on a superoxol-etched n-germanium surface with a subsequent three- 

 minute soak in H2O2 . This characteristic was extremely sensitive to 

 variation in point pressure. 



Miller has also referred to output anomalies of types (2) and (3), which 

 are usually associated with close point spacing in conventional point- 

 contact transistors. Such types of anomaly have been observed in un- 

 formed units (with high average alpha) made on HF treated surfaces. 



3.3.5 Floating Potential Measurements 



In all cases where the /c(0, —10) and average alpha on etched sur- 

 faces are increased by the HF or solder flux treatment, these increases 

 are accompanied by an increase in the magnitude of the floating poten- 

 tial near the reverse-biased collector. In Fig. 12 the magnitude of the 

 floating potential Vp of a sharp tungsten probe near the reverse-biased 

 collector is shown as a function of r, the distance of the probe from the 

 collector (r is approximately the distance between the center of the two 

 point contacts). The surface used in this experiment was prepared by 

 chemical polish for three minutes in CP4 and subsequent storing in room 

 air for sixteen hours. This provided a smooth surface which resembled, 

 at least with regard to electrical characteristics, a freshly etched super- 

 oxol surface. 



Curve I represents the potential-distance plot for an unformed BeCu 

 point on the aged superoxol-etched surface. Curve II represents a similar 

 plot for an unformed BeCu point taken after the surface was given a 

 ten-minute soak in 24 per cent HF. 



