Defect sensitive etching of hexagonal boron nitride single crystals

Abstract

Defect sensitive etching (DSE) was developed to estimate the density of non-basal plane dislocations in hexagonal boron nitride (hBN) single crystals. The crystals employed in this study were precipitated by slowly cooling (2–4 °C/h) a nickel-chromium flux saturated with hBN from 1500 °C under 1 bar of flowing nitrogen. On the (0001) planes, hexagonal-shaped etch pits were formed by etching the crystals in a eutectic mixture of NaOH and KOH between 450 °C and 525 °C for 1–2 min. There were three types of pits: pointed bottom, flat bottom, and mixed shape pits. Cross-sectional transmission electron microscopy revealed that the pointed bottom etch pits examined were associated with threading dislocations. All of these dislocations had an a-type burgers vector (i.e., they were edge dislocations, since the line direction is perpendicular to the [211¯0]-type direction). The pit widths were much wider than the pit depths as measured by atomic force microscopy, indicating the lateral etch rate was much faster than the vertical etch rate. From an Arrhenius plot of the log of the etch rate versus the inverse temperature, the activation energy was approximately 60 kJ/mol. This work demonstrates that DSE is an effective method for locating threading dislocations in hBN and estimating their densities.

Ellipsometry Study of Hexagonal Boron Nitride Using Synchrotron Radiation: Transparency Window in the Far‐UVC

“…[ 61 ] Transmission electron microscopy (TEM) measurements revealed the formation of etch pits where dislocations intersect the surface, with an etch pit density of 5 10 cm −2 , upon defect sensitive etching on h ‐BN crystals grown by this technique. [ 62 ]…”

“…[61] Transmission electron microscopy (TEM) measurements revealed the formation of etch pits where dislocations intersect the surface, with an etch pit density of 5 10 cm À2 , upon defect sensitive etching on h-BN crystals grown by this technique. [62] Spectroscopic ellipsometry was performed using two different instruments. For the energy region up to 6.5 eV, a commercial variable-angle ellipsometer (Woollam VASE) was used.…”

Molten Barium Hydroxide as Defect Selective Drop Etchant for Dislocation Analysis on Aluminum Nitride Layers

“…[12][13][14][15][16] In many investigations, it is, therefore, a standard method for determining dislocation densities in many substrate materials including SiC, GaN, AlN, BN, and AlGaN. [12,[17][18][19][20][21] Molten salts are generally preferred, as the use of hot aqueous solutions leads to low etching rates and low sensitivity. [20] Various investigations on defect selective etching of GaN were performed by the Institute of High-Pressure Physics (Warsaw) in DOI: 10.1002/pssa.202100707…”

“…[ 12–16 ] In many investigations, it is, therefore, a standard method for determining dislocation densities in many substrate materials including SiC, GaN, AlN, BN, and AlGaN. [ 12,17–21 ] Molten salts are generally preferred, as the use of hot aqueous solutions leads to low etching rates and low sensitivity. [ 20 ]…”

Phonons of hexagonal BN under pressure: Effects of isotopic composition

“…[18] The low-temperature photoluminescence spectra have multiple narrow phonon replicas above 5.75 eV, which are present only in high-quality h-BN [23]. The etch pit density was 5 × 10 7 cm −2 on h-BN crystals grown by this technique, the pits forming where dislocations (identified by transmission electron microscopy) intersect the surface upon defect-sensitive etching [32].…”