Hydrothermal Growth of Zinc Oxide Crystals.

Abstract

This projeoc has been aooomplished as a part .of the Air Foroe Mmfao ,, ing Nothoms Program, the primary objeotive of whioh is to develop, on a timely bas is* indsaoturig prooeusee, teohiques and equipment for use in ooonoidol" produotion of U3 materials and oomponents. The prograa enompases the rollowirg te*.noal areas.Des•gn of pilot line for 2hO oryutals by the molten malt toohnique, the hydrotheial rowth of large B2O orystale, the hydrothe•aml growth of doped IO rystals.Staptions oonoeming additional INafaobaring -thods developmmnt required on this or other subjeots will be appreoiated.Mei technical report has been reviewed ad in apprved. S..... ASSTRACrA pilot line for the production of large high quality ZOO single crystals was established and many large crystals were produed. The pilot line can be divided into two units, 1) a molta salt line for the production of seed plates to ba used in 2) the hydrothermal crystal growth pilot line. The design and construction ot both lines were successfully completed and functioned as planned.The molten salt crystal growth effort was not as successful as had been anticipated.Large area, high quality crystal* could not be made reproducibly by this technique.The moet -upa-eat reasons for the failure to do so rests in thermal gradient control during the growth cycle and/or the presence or absence of impurities to the melt.Although these problems ware not v-ospletely resolved, the valtel salt pilot line did yield sufficient ?lates for the initilt portion of the hydrotherual crystal growth program.Once growth conditions and procedures were established in the hydrothermal pilot line, the hydrotherually grown crystals were sectioned and used as seeds for subsequent runs. The area of the crystals were increased by continued growth until large high quality crystals weighing more than 150 grass could be grown on such seeds within zeasonable operating times.One problem arose which had not been encountered in previous hydrothermal systems.It was found that the silver liner or can was corrosively attacked during the course of the growth cycle.The silver which was dissolved in the fluid in the nutrient chamber would also be deposited in the crystals in the growth chamber.=is problem was solved by adding a reducing agent (metallic zinc) to the reactants. The cause of the corrosion apparently is due to the presence of oxygen dissolved in the solvent and as air entrapped in closure of the can.The reason this phcnomenon had not been observed in other small systems using noble metal liners is that no other similar system has been scaledup to the ZnO size.The solution of this problem for the ZnO case will undoubtedly be of value to other large hydrothermal crystal growth sys-:I teaus.In addition to the growth of the large crystals many smaller crystals were grown which were doped with copper to give resistivities in the 102 --D lO0 ýcm range. This is the range most desirable for ac•ustical an--plifier devices.Other doping studies indicate a wide variation of resistivities within the virgi...

Hydrothermal growth and characterization of nitrogen-doped ZnO crystals

“…The hydrothermal method has been known as a method to grow highly crystalline and large-size crystals for ZnO substrates under a relatively low temperature with low cost [8][9][10][11][12]. In this paper, we report the growth of nitrogendoped ZnO single crystals by the hydrothermal method and characterization of the grown crystals by chemical analysis, photoluminescence (PL) and Hall measurements.…”

Removing Inclusions From Crystals by Gradient Techniques

“…Powers (74, 75) observed the cracking of a sucrose crystal during growth and the subsequent suck-back of mother liquor into the crack. Veils and cracks are also found in conjunction in ruby grown hydrothermally (57). Cracks began emanating from rounded solvent inclusions at 140" C. Within a few minutes with continued heating, the cracks had healed to leave sheets of tiny droplets-veils.…”

Hydrothermal growth of Ti:sapphire (Ti3+: Al2O3) laser crystals

“…It is well known that sapphire (a-Al 2 O 3 ) can be grown in alkaline solution with a forward temperature gradient [9][10]. The chemistry is assumed to be…”

“…It has been demonstrated that crystal growth from hydrothermal solutions is one of the best technologies to achieve high quality crystals (such as a-quartz and ZnO) [5][6][7]. Hydrothermal growth of pure sapphire and ruby (chromium-doped sapphire, Cr 3+ :Al 2 O 3 ) was reported in 1960s [8][9][10]; however, there is no report on hydrothermal synthesis of Ti:sapphire crystals until now. In this paper, we describe the hydrothermal growth of titanium(III)-doped a-Al 2 O 3 for the first time.…”