ENGINEERING RESEARCH INSTITUTE UNIVERSITY OF MICHIGAN ANN ARBOR QUARTERLY REPORT NO. 1 Period 5 March to 5 June, 1952 and Additional Data to 4 August, 1952 ELECTRON DIFFRACTION INVESTIGATION OF PHOTOCONDUCTIVE CRYSTALLINE IEAD SULFID E.SURFACES By L. O0 BROCKWAY Professor! Chemistry ProJect 2037 AIR RESEARCH AND DEVELOPMENT COMMAND, U. S. AIR FORCE COreRmACT NO. AF 18(600)-u75, E.O. NO. 35550-2 August, 1952

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ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN ELECTRON DIFFACTION INVESTIGATIONS OF PHDTOCONDUCTIVE CRYSTALLZINE LEAD SULFIDE SURFACES INTRODUCTION On 20 August,. 1951 Professor Brockway was asked by the Physical Sciences Division of the National Research Council to consider whether electron diffraction methods could offer material assistance in a fundamental study of the properties of photoconductive lead sulfide films, with the understnding that the then C.muanding General of the Air Research and Development Cond of the U. S. Air Force had requested the National Research Council to suggest research projects suitable for support by the Air Force. After consultation with Professor Brian O'Brien of the Institute of Optics at the University of Rochester and Professor G.B.B.M. Sutherland of the University of Michigan and after examination of the literature, Professor Brockway concluded that no systematic study had ever been made of the composition and structure of partially oxidized lead sulfide surfaces in relation to variations in the method of preparation and in the physical properties of the films. Since this aspect of the problem is important for a fundamental understanding..of the behavior of the films and since it is -susceptible to study by electron diffraction and microscope methodes, a proposal was drafted. After review by the Physical Sciences Division of NRC, it was submitted to AHDC in October 1951. A tentative agreement was reached with an experienced electron diffraction inveetigator to work full-time oi the project. After three months he could wait no longer and withdrew. Nlo further efforts were made to obtain personnel in the absence of a caontract. On 14 January, 1952, Purchase.',equest No. 264865 was received, the proposal was re-submitted on 23 January, and contract AF 18(.600-175 was signed as of 29 February, 1952.

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN ACTIvITViRB DERS T= COUTRkCT zquipuient As provided in the proposal and th-"-ntract, rdru were placed for an RCA electron diffraction unit and a high vauum evapotor. The diffraction unit required ae a replacement for a similar unit in this laboratory was delivered on 28 April and has been assembled, tested, and placed in operation, It has been used for prelilinary work in the investigation of lead sulfide surfaces. It has also been used extensively to date in connection with Project 2020 under Air Force Contract No. AF 31(616)-23,.oOo. R46 3 Br-O1, Developent of Procedures for the Identification of Minor Phases in Heat-Resistant Alloys by Elec. tron Diffract ion, a project which has been very productive. The high-vacuum evaporator was delivered on 28 July and placed in operation for preparing condensed films of lead sulfide and surface replicas for electron microsope examination. Personnel After the contract date, negotiations were renewed for an expe4''enced full-time investigator for the proJect. By that time the only source was graduate students with x-ray and electron diffraction training who expected to receive Ph.D. degrees in June 1952 or later. Offers were made to several men amounting to $6000 a year, with thirty days." leave, a top figure in academic labortorie for new Ph.D. research men, since the 50 per cent differential above new instructors is barely tolerable. The competition with industrial reeearch laboratories for trained en has been especially keen in 1952, mny current PhD. graduates in physics an physical chemistry-have taken Jobs with starting salaries ranging from $750o to $8o00. The freedom of academic laboratories, including free publications of results in particular, is the advantage that universities can offer to offset the higher salary in industry. Two promiinag candidates (from the Polytechnic Institute of Brooklyn and Iawa State College, respectively) were still considering the position when the demand deecribed below was made in early June that the present contract be classified and publication of reslts be restricted. In fairness to the men it was admitted that the classificatian status of the contract had ce under queoti s and they eiately acopted idutrial jobe.

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN In this situation it has been imposeible to interest fully trained men; the prospect of working at a reduced salary without the advantage of enhancing professional reputation through publications is without attraction. The alternative is the assignment of one or xzre graduate students still in training with a correspondingly lower rate of progress on the project. One graduate student and one part-time assistant have been assigned to the project as of 15 September.,1952. In the meantime the project supervisor and other laboratory personnel have assembled the equipment and made tests and adjustments for the handling of lead sulfide surfaces, using preliminary specimens Research P The third activity started on signing of the contract in ad?dit ion to procurement of equipment and personnel was the setting up of a program for the initial investigations.. Preliminary tests were started on the behavior of oxidized lead sulfide surfaces in electron beam with reference to charging up effects. This was to be followed by determinai tions of particle size in different films, of the single or aultiple crystalline character of the particles, of the chemical composition, and of the extent to which oxidized phases cover the particles. Later work was planned for investigation of possible preferred orientation of the lead sulfide crystals on the glass supPqrt.and also of the oxidized phases with reespect to the lead sulfide; the effect of intrducing various pre ferred orientations was to be tested on films condensed onto vubstrates consisting of massive single crystals of nonconducting minerals. The tests on composition,distribution,of the two or more phases, particle size, and orientatin need. to be carried out in a maRner to de. tect differences in these chemical ad structural properties due to the changes in the procedures used in preparing the films. At the same time correlations are required with changes in the optical and electrical properties of the films ThLs correlation with physical properties was to be supervised and in part carried out by Professor Brian.iarien, It as agreed that while mogt of the films used should be prepared in Ann Arbor it would be in keeping with sound research practice to have sme disecussion with, and perhaps obtain some specimens from the two.companies engaged in-production.of lead sulfide films, i.e., East.Kodak. Company and Photoswitch Incaprpwated. The first visit was aaraned with Photoewitch because this.compahy alreadyhad a contract with the Air Force. On. 1 June Professor Brockway met at Phooswitch, in Cambride., with Professar Wayne Nottingham of the Masseachusettes Institute of Technology, Dr. Raymgnd I~cee of

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN Photoswitch, and with the president of Photoswitch. Professor Notti ham spoke for -Photoswitch. Professor Nottingham expressed surprise at the existence of the present contract and maintained that it was previously unmkrwn to the Photoswitch contact at Wright Air Development Center. He suggested at first that the electron diffraction work of Professor Lark-Horowitz of Purdue TUniversity performed on a service basis for Photoswitch had exhausted the necessary investigation with electrons, but later agreed that a more systematic and thorough study would be required for underfstanding the fundamental nature of the filmo A plausible theory had been based on the identif ication of lanarkite on certain fils combined with assumptions about particle-size distribution and the distribution of the lanarkite phase. Professor Nottingham stated further that the methods of prepaation are a comercial aLd military secret, that Phbtoswitch wants to restrict publication inthis field in order to maintain comerc ial control, that he could not see how work under the present contract could be fitted into the overall lead sulfide film program unless it were classif~d~,and that he would ask the Air Force to classify this contract if it were continued. It is now apparent that the request originating with Photoswitah that the present contract'te claesified or cancelled has been lade. Classifications will so hinder the work t$at this laboratory would have no interest in the project in the absence of military urgency for the work. RECOMMENATIONS It is recomended that this laboratory be permitted to accum_late fundamental aud. basie.information or- the composi-tion ans structure of lead sulfide films in relation to. their.physic al propert.es and methode- of preparation, and. that publication of results be pe-mitted while avoiding the publication of information dealig. wlth the details of preparation of films. An agreement should be reached whereby the inter* ests of Photoswitch are recognized without prohibiting all fundamental work in the field.

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