Floating zone furnace equipped with a high power laser of 1 kW composed of five smart beams

Abstract

A floating zone furnace is a powerful tool for single crystal growth. Here, we report the floating zone furnace using a high power diode laser of 1kW composed of five 200 Watt heating beams. The five beams with the designed irradiation intensity distribution enable the melt-growth of single crystals for refractory materials having a high melting temperature above 2000°C, volatile materials and even incongruent materials. The power of five beams in the horizontal plane provides uniform intensity in the outer circumference of the raw material rods, while the vertical direction power of five beams can be made to have a bell shape irradiation intensity so as to relax residual thermal stress in the grown single crystal. The present furnace enables one to directly monitor the temperature of the hot spot of raw material and the molten zone within a 1 mm diameter. Such an in-situ monitoring function of the temperature on the molten zone greatly enhances the controllability for optimizing the crystal growth condition.Ha(Y) on the Y-axis is measured by moving the thermocouple on the Y-axis direction. The obtained Ha(Y) on the Y-axis has a gaussian shape. The position at 10% of the maximum intensity of the halogen lamp in the Y direction is ±25mm from the center at Y-axis. The Ha(X) along the X-axis is the same as the Ha(Y) along the Y-axis. The green dashed line is calculated by assuming the four irradiation light beams with the same Ha(X). With a confocal elliptical mirror in the case of using two halogen lamps, the uniformity will be even worse, less than 50%. On the other hand, the red solid line in Fig. 3, which was calculated and reported also by Ito et al.[5], shows irradiation intensity distribution in the azimuthal direction of the raw material rod in both cases of type A with a flat shape and type B with a gaussian shape in the case of using LFZ. In this case, high uniformity of 95% or more can be ensured over 360° around the raw material rod. For the actual crystal growth procedure in

Topological Quantum Materials from the Viewpoint of Chemistry

“…With several important and interesting materials such as carbides, borides, silicides, intermetallic Heusler topological compounds the future of OFZ in topological research appears bright. Recently, single crystals of some topological materials like SmB6, [168][169][170] CoSi, 142 and Co2MnAl 171 have been grown using this technique (see inset of Figure 14). Inset shows an as-grown SmB6 crystal; reprinted with permission from ref.…”

Laser Floating Zone Growth: Overview, Singular Materials, Broad Applications, and Future Perspectives

“…Thus, the use of various lasers enables uniform irradiation intensity distribution on the periphery of the raw material. Moreover, a vertical irradiation intensity can be designed to exhibit a flat or bell-shape distribution to improve relaxation of residual thermal strain in the grown crystal [22,32]. Nowadays, the Crystal Systems Corporation (Hokuto, Yamanashi, Japan) commercializes a laser floating zone furnace that provides a total laser power output of 5 kW, employing five laser diodes emitting at a wavelength of 808 nm [33].…”

“…In addition, these authors studied the effects of the number of laser diodes (3 to 8) on the quality of radial heating. A similar apparatus was recently employed by Kaneko NS Tokura, in 2020 [32], to grow refractory (Al 2 O 3 :Cr, SmB 6 ), incongruent melting (Ba 2 Co 2 Fe 12 O 22 ) and volatile (Nd 2 Mo 2 O 7 , SrRuO 3 ) materials by LDFZ, employing five laser diodes emitting at 940-nm wavelength with a total power of 1 kW. Thus, the use of various lasers enables uniform irradiation intensity distribution on the periphery of the raw material.…”

“…In addition, similar equipment from Quantum Design International (San Diego, CA, USA) allows monitoring the temperature in the range 1173-3273 K while achieving a maximum laser output power of 2 kW from five laser diodes [34]. Ito et al, in 2013 [22], provided with five laser diodes, allowing a uniform irradiation intensity distribution on the periphery of the raw material [22,32].…”

“…Lately, as was mentioned in Section 2, equipment setup advances providing high-pressure [23] or uniform radial heating by using various laser diodes [22,32] has allowed us to synthesize volatile ( [192]. Likewise, for growing crystals of the pyrochlore-type Nd 2 Mo 2 O 7 (NMO), suitable for Hall effect sensors, only a slight pressure of 1 atmosphere is needed, as recently reported by Kaneko and Tokura, in 2020 [32], to promote the re-evaporation of MoO 2 by rapidly increasing the temperature of the molten zone. These authors have also grown SrRuO 3 (SRO), an archetypal perovskite ferromagnetic metal, which also presents the deposit of RuO 2 near the melting point.…”