VACUUM

Classified Abstracts

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I I I - Vacuum Processing T e c h n i q u e s - III

3 ° - - E V A P O R A T I O N - - 30

New Types of Interference Filters of Greater Areas and Higher Contrast See Abstract No 235/I

Thickness Measurements of Thin Films by Multiple Beam Interferometry Umted Stales A brief discussion of Flzeau fringes and fringes of equal chromatic order Is followed by da ta on

the thickness measurement of th in films of silver, ba r ium stearate, and collodion by means of fringes of equal chromatic order Measurements were made on films ranging in thickness f rom about 100 to 2,000 A with a probable accuracy of 15-30% Mostly the films to be subjected to mterferometr ic measurement were no t formed directly on the mmroscope slide bu t were prepared on some other suppor t using collodion as a subs t ra te to facilitate the t ransfer to the microscope slide In the course of the exper iments the authors invest igated whether measurements on a collodion film of the type mentioned would indicate any change as a result of the s tr ipping operat ion lequlred to facilitate the t ransfer A microscope shde dipped m 1 ~/ collodion solution was drained, dried and cut in half lengthwise One half was s tr ipped and transterred to a second slide Both par t s were scratched in three corresponding planes and the thickness was measured, wi th the results shown in the table pa r t ly reproduced belo~

Combamson of Stropped and Unshipped ;dins

Film Yhzdness ( A)

Scratch U ~stnpped Str2pped

1 1310 1276 2 144() 1434 3 1507 1450

I

Somma~re Des recherches ont ete faxtes sur la technique d ' lnterferometrle pour son emplol dans les mesures d 'epalsseur de couches de collodion, membranes de plast lque ctc

Usefulness of the Polarlmetnc Method for the Determination of the Refractive Index and of the Thickness of one Thin Film on Glass or on Metal

See Abst rac t No 234/I

On Polartsatxon by Transmission with Particular Reference to Selenium Films m the Infra-Red See Abst rac t No 233/I

Two-Layer Anti-Reflection Coatings for Glass in the Near Infra-Red Umted States Three types of two-layer anti-reflection coatings capable of producing zero reflectance on glass

of index 1 51 are discussed All three types consist of a high-index inner film and a low-index outer film and use the same low-index film material (MgF 2 wi th h i = 1 38) bu t various high-index coatings The first design, consisting of two quar ter -wave films, requires n 2 = 1 7 for producing zero reflectance on glass at lt~ wavelength The reflectance mi n i m um of such double quar te r -wave coatings is ext remely sensitive to thickness var iat ion of the low-index film and very much less influenced by mismatching of the high-index coating The second type of coating consists of a th ln high-Index (t2<)`/4) and a thick low-index ( t l>) , /4 ) film This combinat ion can yield zero reflectance for all values of n2> 1 7 The third coating type uses one half-wave and one quar ter -wave film Wi th coatings of this type two reflection minima which become zero for n 2 = 1 9 can be obtained Experi- menta l coatings of the three types were used for anti-reflecting glass in the near infra-red The coatings were prepared by high vacuum evaporat ion of MgF,, SIO, and Ce02

(Authors) Somma*re Trois types de dep6ts, form6s de deux films Antl-Rdflexion capables de p rodmre une r6flexxon nulle sur verre d'lndlce 1 51, sont discutes

Structure and Texture of Evaporated Nickel Films Determined by the Electron Microscope and Electron Diffraction See Abst rac t No 241/I

An Electron-Diffraction Examination of Thin Fdms of Lithium Fluoride and Copper Prepared by Vacuum Evaporation Umted K , ngdom The investigation reported is concerned wi th stress sys tems In thin films of h th lum fluoride

and copper deposited on a cellulose subs t ra te by evaporat ion at a pressure of 10 -5 m m H g The films were

Abstract No and References

153/III

154/III

Report by T W Bartlett &

F L Ball A E C Rep No

K-1135 June 1954

155/III

156/III

157/III

Arblcle by J T Cox G Hass &

R. F Rowntree Vacuum

4, Oct 1954 445-455

158/III

159/III

O~.tob~r, 1954 Vacuum 532 Vol I V No 4