Polar oxysulfide for nonlinear optical applications
Single crystals of a new noncentrosymmetric polar oxysulfide SrZn 2 S 2 O (s.g. Pmn2 1 ) grown in a eutectic KF-KCl flux with unusual wurtzite-like slabs consisting of close-packed corrugated double layers of ZnS 3 O tetrahedra vertically separated from each other by Sr atoms and methods of making same.
1. A method for synthesizing the compound SrZn 2 S 2 O comprising:
loading a silver tube with 1 mmol of SrO, 1 mmol of Zn, 1 mmol of S, 3.4 mmol of KF, and 4.1 mmol of KCl;
placing the silver tube in a silica tube that was evacuated to 10 −4 Pa and sealed;
heating the silver tube in a tube furnace to 900° C. at 5° C./min, held for 24 h, and cooled to 600° C. at 0.17° C./min;
making a molten salt from a eutectic KF-KCl mixture, wherein SrO, Zn and S are dissolved in the eutectic KF-KCL mixture to form a flux;
wherein the method produces SrZn 2 S 2 O containing at least one wurtzite-like slab comprising at least one corrugated double layer of ZnS 3 O tetrahedra; and
the SrZn 2 S 2 O is a direct band gap semiconductor.
2. The method of claim 1 , further comprising, extracting the compound from the flux by dissolving the flux in water followed by sonication.
3. The method for synthesizing the compound SrZn 2 S 2 O of claim 1 , wherein the at least one corrugated double layer of ZnS 3 O tetrahedra contains vertically separated by Sr 2+ ions wherein an O/S anion ordered arrangement provides two distinct orientations of the ZnS 3 O tetrahedra.
4. The method for synthesizing the compound SrZn 2 S 2 O of claim 1 , wherein the compound crystalizes in noncentrosymmetric polar space group Pmn2 1 .
5. The method for synthesizing the compound SrZn 2 S 2 O of claim 1 , wherein the compound forms colorless, transparent crystals.
6. The method for synthesizing the compound SrZn 2 S 2 O of claim 1 , wherein the compound has a band gap of 3.86 eV.
7. The method for synthesizing the compound SrZn 2 S 2 O of claim 1 , wherein the compound is stable up to 650° C. in O 2 gas atmosphere.
8. The method for synthesizing the compound SrZn 2 S 2 O of claim 1 , wherein the compound is phase matchable with twice a SHG intensity of potassium dihydrogen phosphate (KDP).
9. The method for synthesizing the compound SrZn 2 S 2 O of claim 1 , wherein the compound has a Sr:Zn:S molar ratio of approximately 1.0:2.0:2.3.
10. The method for synthesizing the compound SrZn 2 S 2 O of claim 1 , wherein the compound has a band gap energy of 3.86 eV.
11. The method for synthesizing the compound SrZn 2 S 2 O of claim 1 , wherein temperatures greater than 1000° C. decompose the SrZn 2 S 2 O compound.