Effect of alkali-metal and some quaternary-ammonium cations on the anodic dissolution of p-Si in fluoride media

Laser-Assisted Formation of Porous Silicon in Diverse Fluoride Solutions: Hexafluorosilicate Deposition

“…The processes involved in the laser-assisted etching of n-type Si in fluoride solutions are illustrated in Figure . Assuming equivalence between electrochemical and laser-assisted etching, several aspects of Figure are unassailable: (1) a hole captured at the surface initiates etching, (2) defects enhance the initiation of etching, , (3) H 2 is a product, (4) electron injection into the Si occurs, − (5) the Si is predominantly H-terminated before, during, and after electrochemical etching − (6) Si is a byproduct, (7) in the presence of K + , Rb + , and Cs + , hexafluorosilicate deposition can occur, , (8) the counter reaction occurs in a spatially separated region of the crystal, and (9) both HF and H can react with the Si atom to be etched . Several aspects are probable but remain to be proved unequivocally: (1) a H + desorbs after hole capture at the surface, (2) a F - attacks the empty site, ,, and (3) the primary etch product reacts with HF to form Si .…”

“…2is a byproduct, (7) in the presence of K + , Rb + , and Cs + , hexafluorosilicate deposition can occur, 34,61 (8) the counter reaction occurs in a spatially separated region of the crystal, 38 and ( 9) both HF and HF 2 can react with the Si atom to be etched. 62 Several aspects are probable but remain to be proved unequivocally: (1) a H + desorbs after hole capture at the surface, 53 (2) a Fattacks the empty site, 53,57,63 and (3) the primary etch product reacts with HF to form SiF 6 2-.…”

“…Boyle et al report an IR spectrum in which the main bands of the thin-film spectrum agree with the bulk spectrum of Badachhape et al In an investigation of the effects of alkali metal and quaternary-ammonium cations on the rate of anodic formation of por-Si, white, sparingly soluble films formed on the external surface in the presence of K + , Rb + , and Cs + . These were identified as hexafluorosilicates. , Stain etching of silicon in HF−oxidant−H 2 O (oxidant = K 2 Cr 2 O 7 , KBrO 3 , or KMnO 4 ) has been studied. , As the concentration of the oxidant is increased, the etch rate increases to a limiting value as the thickness of the K 2 SiF 6 increases. The layer thickens with reaction time until a point is reached when it stops further reaction by preventing the liquid reactants from making contact with the silicon surface.…”

“…These were identified as hexafluorosilicates. 33,34 has been studied. 35,36 As the concentration of the oxidant is increased, the etch rate increases to a limiting value as the thickness of the K 2 SiF 6 increases.…”

Anodic current transient for n-Si|SiO2 electrodes in HF solution: the relationship between the current and the interface structure

“…The current rises when the dissolution reaches the SijSiO 2 interface and almost ends when the surface becomes hydrogen-terminated. Besides the interest in what information on oxides can be obtained from the analysis of the current transient [11][12][13], there has been much interest in whether the properties of the Si surfaces after the current transient are similar to those obtained by the chemical process [14][15][16][17][18][19][20][21][22][23][24]. Although the anodic current transient has been known for more than 20 years [25,26], its origin is still unclear.…”