The ingots were polycrystalline because of the severe growth conditions during synthesis. Considerably more growth stability would be required for single crystal growth.
The ever-increasing interest in the use of IV-VI compounds, particularly PbTe and Pbl-~SnxTe, for IR detectors and the success demonstrated in the use of metalorganics in preparing III-V and II-VI compounds and alloys (1) prompted a study to extend the metalorganic chemical vapor deposition (CVD) technique to the preparation of IV-VI compounds also. Growth studies were performed on PbTe and on single-crystal insulating substrates transparent in the visible part of the spectrum. The transparent substrates were used in order to help in determining the onset of crystal growth as evidenced by a darkening of the substrate and to facilitate optical studies and microprobe analyses of the crystals formed. These substrates included mechanically polished A1203, MgA1204, and BaF2, and freshly cleaved (in air) MgO, NaC1, CaF2, and BaF2, BaF2 was the primary insulator used in these investigations since in thin wafer form it is transparent to 11-1'2 #m radiation, is more stable than NaC1 at temperatures ,~625~ and matches the thermal expansion of the IV-VI's relatively closely (2).The metalorganic compounds used in this study, some of their pertinent properties, and the suppliers are listed in Table I.The Pb, Sn, and Te compounds were used as received in stainless steel bubblers except for purging with tI2 carrier gas prior to use in film growth experiments. The bubblers were maintained at room temperatuze during film growth. Pd-purified It2 at a total flow of about 10 liters/min was used as the carrier gas in the deposition experiments. HeS and H2Se were at a minimum purity of 99.5 and 98.0%, respectively (Matheson Gas Products, East Rutherford, New Jersey).BaF2 and CaF2 were purchased from the Harshaw Chemical Company (Solon, Ohio). Rockwell polished single-crystal BaF2 windows and BaF2 and CaF2 wafers cleaved from 1 in. diameter rods were used as substrates. Cleaving into (lll)-oriented substrate blanks was performed just prior to use in a film growth experiment. The a-A1203 was Czochralski material from Union Carbide Corporation (San Diego, California) and polished by Insaco (Quakertown, Pennsylvania). The MgA1204 was produced and polished by Union Carbide Corporation. The NaC1 and MgO were single crystals that were cleaved just before use.The PbTe substrates were all wafers sawed from crystals obtained from Electronic Materials Corpora-* Electrochemical Society Active Member.
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