Article comprising a semiconducting material
View Patent ↗Single crystals of the new semiconducting oxychalcogenide phase were synthesized using a novel crystal growth method. The crystals had low defects and homogeneous composition as characterized by single crystal X-ray diffraction and scanning electron microscopy, respectively. Heat capacity and resistivity measurements were in agreement with the calculated band structure calculations indicating semiconductivity, with a band gap of about 3 eV.
1. A method for forming an oxychalcogenide composition, comprising:
providing a mixture having a molar ratio of about 20 R:1 RO:1 X, where R is an alkaline earth metal cation, X is an elemental chalcogen, and O is oxygen;
heating the mixture until the mixture melts;
fluxing the melted mixture at least at the melting point for about 10 hours;
allowing the mixture to cool; and
removing one or more oxychalcogenide crystals from the mixture, where the one or more oxychalcogenide crystals, comprise:
a tetragonal crystal of repeating units of RX′ and RO;
wherein R is an alkaline earth metal cation, X′ is an anionic chalcogen, and O is oxygen;
wherein the alkaline earth metal cation of RO is integrated into a crystalline structure with the unit of RX′; and
wherein the R:X′ molar ratio is about 2:1.
2. The method of claim 1 , wherein the mixture is heated to about 1,000° C.
3. The method of claim 1 , wherein the mixture is cooled to about 820° C. over a period of time ranging from about 24 hours to about 150 hours.
4. The method of claim 1 , wherein the oxychalcogenide composition is Ba 2 TeO.
5. The method of claim 1 , wherein the elemental chalcogen comprises tellurium.
6. The method of claim 1 , further comprising adding a doping agent other than the elemental chalcogen to the mixture such that a doping anion is substituted for a portion of the anionic chalcogen of the one or more oxychalcogenide crystals.
7. The method of claim 6 , wherein the doping agent comprises a pnictogen.
8. The method of claim 7 , wherein the pnictogen comprises bismuth.
9. A method for forming an oxychalcogenide composition, comprising:
providing a mixture having a molar ratio of about 20 R:1 RO:1 X, where R is an alkaline earth metal cation, X is an elemental chalcogen, and O is oxygen;
placing the mixture in a crucible;
sealing the crucible;
heating the mixture until the mixture melts;
fluxing the melted mixture at least at the melting point for about 10 hours;
allowing the mixture to cool; and
removing one or more oxychalcogenide crystals from the mixture, where the one or more oxychalcogenide crystals, comprise:
a tetragonal crystal of repeating units of RX′ and RO;
wherein R is an alkaline earth metal cation, X′ is an anionic chalcogen, and O is oxygen;
wherein the alkaline earth metal cation of RO is integrated into a crystalline structure with the unit of RX′; and
wherein the R:X′ molar ratio is about 2:1.
10. The method of claim 9 , wherein the step of heating the mixture until the mixture melts is performed to a temperature of 1000° C.
11. The method of claim 9 , wherein the step of allowing the mixture to cool is performed at a rate of 1.2 degrees per hour to 7.4 degrees per hour.
12. The method of claim 9 , wherein the step of placing the mixture into the crucible is performed in an inert atmosphere.
13. The method of claim 12 , wherein the inert atmosphere is a single inert gas or a mixture of inert gases.
14. The method of claim 13 , wherein the single inert gas is argon.
15. The method of claim 12 , wherein the step of placing the mixture into the crucible is performed at an elevated pressure.
16. The method of claim 9 , further comprising doping the mixture, wherein the doping of the mixture comprises:
adding a pnictogen to the mixture such that the pnictogen is present in the one or more oxychalcogenide crystals at an amount up to about 20 atomic percent of the anionic chalcogen.