Conventional Crucibles Research Articles

A cooling fin to enhance the efficiency of crystal growth by physical vapor transport

In general for crystal growth, material should deposit on the seed crystal and not on any adjacent supporting structures. This efficiently uses the source material and avoids the possibility of spurious polycrystals encroaching on, and interfering with the single crystal growth. In this paper, a new crucible design with a cooling fin in contact with the seed was simulated and experimentally demonstrated on the physical vapor transport (PVT) crystal growth of scandium nitride (ScN). The heat transfer of the growth cavity for a conventional crucible and a modified crucible with the cooling fin were modeled theoretically via computational fluid dynamics (CFD) with FLUENT. The CFD results showed that the seed in the modified crucible was approximately 10 °C cooler than the crucible lid, while in the conventional crucible the temperature of the seed and lid were uniform. The experimental results showed that increasing the temperature gradient between the source and the seed by employing the cooling fin led to a dramatic increase in the growth rate of ScN on the seed and reduced growth on the lid. The relative growth rates were 80% and 20% on the seed and lid respectively, in the modified crucible, compared to 25% and 75% with the conventional crucible. Thus, the modified crucible improved the process by increasing the growth rate of single crystals grown by sublimation.

The Role of Porous Graphite Plate for High Quality SiC Crystal Growth by PVT Method

The present research is focused to investigate a role of the porous graphite (PG) plate that could improve the quality of 4H-SiC crystal. The grown crystal in porous graphite inserted crucible showed the lower intensity of Al, B and Ti impurity concentration than SiC crystal grown in conventional crucible. The porous graphite plate before and after the growth process has been investigated by a Raman spectroscopy and a photoluminescence spectrum (PL). According to the analysis result, it was confirmed that the porous graphite plate had the effect of suppressing impurities supplied to SiC single crystal during the growth process.

Effect of Porous Graphite for High Quality SiC Crystal Growth by PVT Method

The effect of the porous graphite plate above the source material on properties of silicon carbide (SiC) crystals grown by Physical Vapor Transport method has been investigated. The porous graphite plate was inserted on source powder to produce a more C-rich for the polytype stability of 4H-SiC crystal and a uniform radial temperature gradient. The dendrite structure obtained from SiC source powder in the crucible with porous graphite plate was more densely formed than that in the conventional crucible. The crystal quality of 4H-SiC single crystals grown in porous graphite inserted crucible was revealed to be better than that of crystal grown SiC crystals in the conventional crucible.

고품질 4H-SiC 단결정 성장을 위한 다공성 흑연 판의 역할

The present research is focused on the effect of porous graphite what is influenced on the 4H-SiC crystal growth by PVT method. We expect that it produces more C-rich and a change of temperature gradient for polytype stability of 4H-SiC crystal as adding the porous graphite in the growth cell. The SiC seeds and high purity SiC source materials were placed on opposite side in a sealed graphite crucible which was surrounded by graphite insulator. The growth temperature was around and the growth pressure was 10~30 Torr of an argon pressure with 5~15 % nitrogen. 2 inch off-axis 4H-SiC with C-face (000-1) was used as a seed material. The porous graphite plate was inserted on SiC powder source to produce a more C-rich for polytype stability of 4H-SiC crystal and uniform radial temperature gradient. While in case of the conventional crucible, various polytypes such as 6H-, 15R-SiC were observed on SiC wafers, only 4H-SiC polytype was observed on SiC wafers prepared in porous graphite inserted crucible. The defect level such as MP and EP density of SiC crystal grown in the conventional crucible was observed to be higher than that of porous graphite inserted crucible. The better crystal quality of SiC grown using porous graphite plate was also confirmed by rocking curve measurement and Raman spectra analysis.

Effect of TaC-Coated Crucible on SiC Single Crystal Growth

The present research was focused to extensively investigate the effect of TaC-coated crucible on the SiC crystal growth and then compare the difference of various properties between SiC crystals grown in conventional graphite crucible and TaC-coated crucible. The bulk growth was conducted around 2200°C of the growth temperature and 40 mbar of an argon atmosphere for the growth pressure. The better crystalline quality was obtained from the crystal grown in TaC-coated crucible. The SiC crystal grown in the TaC-coated crucible exhibited superior characteristics than SiC crystal grown in the conventional crucible in terms of the crystal quality and defect density. Furthermore, nitrogen incorporation in SiC crystal grown in the TaC-coated crucible was definitely decreased.

The Effect of Modified Crucible Design and Seed Attachment on SiC Crystal Grown by PVT

The present research was focused to investigate the effect of internal crucible design that influenced the 4H-SiC crystal growth onto a 6H-SiC seed by PVT method. The crucible design was modified to produce a uniform radial temperature gradient in the growth cell. The seed attachment was also modified with a use of polycrystalline SiC plate. The crystal quality of 4H-SiC single crystals grown in modified crucible and grown with modified seed attachment was revealed to be better than that of crystal grown in conventional crucible. The full width at half maximum (FWHM) values of grown SiC crystals in the conventional crucible, the modified seed attachment and the modified crucible were 285 arcsec, 134 arcsec and 128 arcsec, respectively. The micropipe density (MPD) of grown SiC crystals in the conventional crucible, the modified seed attachment and the modified crucible were 101ea/cm^2, 81ea/cm^2 and 42ea/cm^2, respectively.

Growth of multicrystalline Si ingots using noncontact crucible method for reduction of stress

Stress control is necessary when preparing high-quality multicrystalline Si ingots using crucibles because crystal defects such as dislocations are mainly generated by stress in the ingots. Conventional crystal growth methods using crucibles cannot control the stress caused by expansion due to the solidification of the Si melt. We proposed a noncontact crucible method using conventional crucibles that reduces the stress in Si multicrystalline ingots. In this method, nucleation occurs on the surface of a Si melt using seed crystals, and crystals grow inside the Si melt without touching the crucible walls. Then, the ingots continue to grow while being slowly pulled upward to ensure that the crystal growth remains in the low-temperature region. The diameter and solidification ratio of the ingots can be controlled by reducing the melt temperature in the low-temperature region and by varying the product of the temperature reduction from the melting point of Si and the total growth time, respectively. A Si ingot with a diameter of 21cm and a solidification ratio of 83% was obtained in a crucible with a diameter of 30cm. We have confirmed that ingot growth in a crucible is feasible, during which the ingot does not come in contact with the crucible walls.

New Crucible Design for SiC Single Crystal Growth by Sublimation

ABSTRACTSiC bulk single crystal growth by sublimation was investigated. A new crucible design, double-walled crucible, was proposed, and its effect was confirmed numerically and experimentally. On the point of heat transfer in a growth cavity, double-walled crucible is better than conventional crucible. With a double-walled crucible, temperature of seed and source surfaces could be kept constant with better uniformity than that with a conventional crucible. It was deduced that a crystal growth rate could be kept constant with flat surface. Furthermore, in case of a double walled crucible, crystal enlarged rapidly with less inclusion. As the results, a double-walled crucible is useful to grow high quality SiC single crystal by sublimation.

Characteristics of PbO–BiO1.5–GaO1.5 Glasses Melted in SnO2 Crucibles

PbO‐BiO1.5‐GaO1.5‐based glasses are good candidates for optical applications, because of some of their interesting characteristics, such as high refraction indices and high transmission in the ultraviolet (UV), visible (VIS), and infrared (IR) regions. A limited stage in the processing of these glasses is the corrosion that is caused by the melt in all currently used conventional crucibles, such as noble metals (platinum or gold) and Al2O3. The absorption of crucible material by the glass composition may reduce the transmission level, the cutoff in the UV‐VIS, and IR regions, and the thermal stability. In this study, a SnO2 crucible has been tested for PbO‐BiO1.5‐GaO1.5 molten glass. Optical and thermal analyses show, in some cases, advantages over the use of platinum and Al2O3 crucibles. A visible cutoff value of 474 nm has been measured, and a longer melting time (850°C for 4 h) results in a significant reduction of the O‐H absorption band at 3.2 μm.

Growth of twin-free InP single cystals by the liquid encapsulated vertical Bridgman technique

We have successfully grown twin-free <100> InP crystals with 50 mm diameter by the liquid encapsulated vertical Bridgman technique. In order to avoid twin formation in the crystals, a flat-bottom crucible was used instead of conventional crucibles with a conical part.

2. An uhv system for in situ preparation and analysis of thin films and surfaces

A versatile uhv system was designed in order to enable the preparation of thin films of different materials and their analysis to be undertaken. It includes various sources for evaporation: a high-power electron gun, conventional crucibles and Knudsen cells. An airlock is available for fast transfer of prepared films and new substrates. By a special sample holder the thin films can be manipulated to different positions for structural analysis by reflection high energy electron diffraction (RHEED), and for chemical analysis by Auger electron spectroscopy (AES) and secondary ion mass spectrometry (SIMS).