Researchers on the U.S. Division of Vitality’s Princeton Plasma Physics Laboratory (PPPL) have developed a brand new theoretical mannequin explaining one technique to make black silicon. The brand new etching mannequin exactly explains how fluorine fuel breaks sure bonds within the silicon extra typically than others, relying on the orientation of the bond on the floor. Black silicon is a vital materials utilized in photo voltaic cells, gentle sensors, antibacterial surfaces and plenty of different purposes.
Black silicon is made when the floor of standard silicon is etched to supply tiny nanoscale pits on the floor. These pits change the colour of the silicon from grey to black and, critically, lure extra gentle, an important function of environment friendly photo voltaic cells.
Whereas there are various methods to make black silicon, together with some that use the charged, fourth state of matter often called plasma, the brand new mannequin focuses on a course of that makes use of solely fluorine fuel. PPPL Postdoctoral Analysis Affiliate Yuri Barsukov mentioned the selection to concentrate on fluorine was intentional: the staff at PPPL needed to fill a spot in publicly accessible analysis. Whereas some papers have been printed in regards to the position of charged particles known as ions within the manufacturing of black silicon, not a lot has been printed in regards to the position of impartial substances, akin to fluorine fuel.
“We now know — with nice specificity — the mechanisms that trigger these pits to kind when fluorine fuel is used,” mentioned Barsukov, one of many authors of a brand new paper in regards to the work. “This type of data, printed publicly and overtly accessible, advantages us all, whether or not we pursue additional data into the essential data that underlines such processes or we search to enhance manufacturing processes.”
Mannequin reveals bonds break primarily based on atom orientation on the floor
The brand new etching mannequin exactly explains how fluorine fuel breaks sure bonds within the silicon extra typically than others, relying on the orientation of the bond on the floor. As silicon is a crystalline materials, atoms bond in a inflexible sample. These bonds may be characterised primarily based on the best way they’re oriented within the sample, with every kind of orientation, or airplane, recognized by a bracketed quantity, akin to (100), (110) or (111).
“In case you etch silicon utilizing fluorine fuel, the etching proceeds alongside (100) and (110) crystal planes however doesn’t etch (111), leading to a tough floor after the etching,” defined Barsukov. Because the fuel etches away on the silicon erratically, pits are created on the floor of the silicon. The rougher the floor, the extra gentle it may take up, making tough black silicon very best for photo voltaic cells. Clean silicon, in distinction, is a perfect floor for creating the atomic-scale patterns mandatory for laptop chips.
“If you wish to etch silicon whereas leaving a easy floor, you must use one other reactant than fluorine. It must be a reactant that etches uniformly all crystalline planes,” Barsukov mentioned.
