A diamond smoothing method of irradiating a laser light onto a raised and recessed surface of a diamond, so as to smooth the raised and recessed surface, by ablation that is caused to occur in the diamond by irradiation of the laser light onto the raised and recessed surface. The method includes: a threshold-energy-density detecting step of irradiating the laser light onto the raised and recessed surface, and changing an irradiation energy density of the laser light, so as to detect a threshold energy density as a lower threshold value of the irradiation energy density that causes the ablation to occur; and a smoothing processing step of executing a smoothing processing by irradiating the laser light onto the raised and recessed surface with a smoothing irradiation energy density that is set to be within a range from 1 to 15 times as large as the threshold energy density.

A monocrystalline germanium wafer that increases the open-circuit voltage of multijunction solar cells, a method for preparing the monocrystalline germanium wafer and a method for preparing an ingot from which the monocrystalline germanium wafer is prepared. The monocrystalline germanium wafer that increases the open-circuit voltage of the bottom cell of multijunction solar cells is prepared by adjusting the amounts of the co-dopants silicon and gallium in the monocrystalline germanium wafer, the ratio of silicon to gallium in the preparation of the monocrystalline germanium.

A monocrystalline germanium wafer that increases the open-circuit voltage of multijunction solar cells, a method for preparing the monocrystalline germanium wafer and a method for preparing an ingot from which the monocrystalline germanium wafer is prepared. The monocrystalline germanium wafer that increases the open-circuit voltage of the bottom cell of multijunction solar cells is prepared by adjusting the amounts of the co-dopants silicon and gallium in the monocrystalline germanium wafer, the ratio of silicon to gallium in the preparation of the monocrystalline germanium.

An electrically conductive GaAs crystal has an atomic concentration of Si more than 1×10.sup.17 cm.sup.−3, wherein density of precipitates having sizes of at least 30 nm contained in the crystal is at most 400 cm.sup.−2. In this case, it is preferable that the conductive GaAs crystal has a dislocation density of at most 2×10.sup.−2 cm.sup.2 or at least 1×10.sup.−3 cm.sup.2.

An electrically conductive GaAs crystal has an atomic concentration of Si more than 1×10.sup.17 cm.sup.−3, wherein density of precipitates having sizes of at least 30 nm contained in the crystal is at most 400 cm.sup.−2. In this case, it is preferable that the conductive GaAs crystal has a dislocation density of at most 2×10.sup.−2 cm.sup.2 or at least 1×10.sup.−3 cm.sup.2.

Provided is a Ga.sub.2O.sub.3-based single crystal substrate capable of achieving a high processing yield. A Ga.sub.2O.sub.3-based single crystal substrate having a crack density of less than 0.05 cracks/cm can be obtained that has as a principal surface thereof a surface rotated 10-150° from the (100) plane, when a rotation direction from the (100) plane to the (001) plane via the (101) plane is defined as positive, having the [010] axis as the rotation axis.

The present invention discloses a method for preparing a bifacial PERC solar cell. The present invention has high photoelectric conversion efficiency, high appearance quality, and high EL yield, and could solve the problems of both scratching and undesirable deposition.

The present disclosure provides a method for facet-selective passivation on each crystal facet of colloidal nanocrystals via solution-phase ligand exchange process, thereby providing highly-passivated and colloidally-stable nanocrystal inks. This ligand exchange strategy separately addresses polar and non-polar facets precluding from deleterious nanocrystal aggregation in the colloid. The method involves the introduction of alkali metal organic complexes during metal halide conventional solution exchanges, and one specific example is Na.sup.+.Ac.sup.−. Alkali metal ions stabilize and passivate non polar facets whereas polar facets are passivated through metal halides. This strategy leads to a significant decrease in nanocrystal aggregation during and after ligand exchange, and to improved photophysical properties stemming from this. The resulting nanocrystal solid films exhibit improved stability, retain their absorption features, and have a minimized Stokes shift.

The present disclosure provides a method for facet-selective passivation on each crystal facet of colloidal nanocrystals via solution-phase ligand exchange process, thereby providing highly-passivated and colloidally-stable nanocrystal inks. This ligand exchange strategy separately addresses polar and non-polar facets precluding from deleterious nanocrystal aggregation in the colloid. The method involves the introduction of alkali metal organic complexes during metal halide conventional solution exchanges, and one specific example is Na.sup.+.Ac.sup.−. Alkali metal ions stabilize and passivate non polar facets whereas polar facets are passivated through metal halides. This strategy leads to a significant decrease in nanocrystal aggregation during and after ligand exchange, and to improved photophysical properties stemming from this. The resulting nanocrystal solid films exhibit improved stability, retain their absorption features, and have a minimized Stokes shift.

A method of processing silicon carbide containing crystalline substrate is provided. The method includes pyrolyzing a surface of the silicon carbide containing crystalline substrate to produce a silicon and carbon containing debris layer over the silicon carbide containing crystalline substrate, and removing the silicon and carbon containing debris layer, wherein the pyrolyzing and the removing is repeated at least once.