The Atomic Layer Deposition of SrB₂O₄ Films Using the Thermally Stable Precursor Bis(tris(pyrazolyl)borate)strontium

Abstract

The atomic layer deposition (ALD) of strontium borate films is carried out using bis(tris(pyrazolyl)borate)strontium (SrTp 2 ) and water as precursors. Self-limiting ALD growth is established at 350 8C with SrTp 2 and water pulse lengths of ! 2.0 s and ! 0.3 s, respectively. An ALD window is observed from 300 to 375 8C, in which the growth rate is 0.47 Šper cycle. The thin film compositions are assessed by elastic recoil detection analysis (ERDA) and X-ray photoelectron spectroscopy (XPS). ERDA suggests compositions of SrB 2 O 4 at growth temperatures of < 350 8C, but the boron/strontium and oxygen/strontium ratios are lower than those of SrB 2 O 4 at 350 and 400 8C. Within the ALD window, hydrogen concentrations range from 0.37(42) to 0.87 (7) at.-%, and the carbon and nitrogen concentrations are below the detection limits. XPS analyses on representative strontium borate thin films show all expected ionizations. X-ray diffraction (XRD) experiments reveal that the as-deposited films are amorphous. The surface morphology is assessed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The rms surface roughness of typical 2 mm  2 mm areas for films deposited at 325 and 350 8C are 0.3 and 0.2 nm, respectively. SEM images of these films show no cracks or pinholes.

Synthesis of Doped, Ternary, and Quaternary Materials by Atomic Layer Deposition: A Review

“…Another alternative approach for the ALD of multicomponent films is to use multiconstituent precursors (Figure c), also referred to as heteronuclear precursors. Such precursors contain multiple metal centersor a metal with a metalloid or nonmetal intended to be incorporated into the film (as in examples like WSi x N y and SrB x O y )thereby guaranteeing the mixing of the atoms in the material and avoiding some of the problems inherent with the supercycle method. However, a major drawback of this method is that the composition of the deposited material is fixed by the structure of the precursor molecule.…”

Unusual stoichiometry control in the atomic layer deposition of manganese borate films from manganese bis(tris(pyrazolyl)borate) and ozone

“…The present work documents the ALD growth of films with the approximate stoichiometries Mn 3 (BO 3 ) 2 and [29][30][31] Replication of the 2:1 boron to cobalt ratio of 2 in the CoB 2 O 4 films implies that 2 physisorbs in a molecular fashion to the surface of the growing film, and is then efficiently transformed by ozone to CoB 2 O 4 . In contrast, 1 and ozone afford films of the approximate composition Mn 3 (BO 3 ) 2 , with an approximate 3:2 manganese to boron stoichiometry.…”

“…25 Film growth was achieved between 640 and 840 C, but a 1:2.5 barium to boron precursor stoichiometry was required to obtain BaB 2 26 We previously reported the atomic layer deposition (ALD) of MB 2 O 4 films (M ¼ Ca, Sr, Ba) between 250 and 400 C using CaTp 2 , SrTp 2 , and Ba(TpEt 2 ) 2 as the metal and boron precursors with water as the oxygen source. [29][30][31] Significantly, the 2:1 boron to metal ratio in the precursors was retained in the MB 2 O 4 films. ALD uniquely enables the stoichiometry control, since the depositions are conducted below the thermal decomposition temperatures of CaTp 2 , SrTp 2 , and Ba(TpEt 2 ) 2 [<400 C (Ref.…”

“…28)]. The intermediate physisorbed precursor monolayers replicate the 2:1 boron to metal precursor stoichiometry in the thin films upon treatment with the water coreactant, and the MB 2 O 4 layers are stable to B 2 O 3 loss at <400 C. [29][30][31] ALD affords conformal coverage of nanoscale features and enables subnanometer control of film thicknesses because of the self-limited growth mechanism. 32,33 ALD can also provide conformal coatings on many nanoscale materials.…”

Stabilization of a Snub Bisphenoidal Environment of Strontium in Bis[3‐(1‐naphthyl)‐5‐(2‐pyridyl)‐2H‐pyrazole]strontium Bis[3‐(1‐naphthyl)‐5‐(2‐pyridyl)pyrazolate] by Strong Hydrogen Bridges

“…Even though pyrazolyl ligands have been most widely used in transition metal chemistry, there are still several complexes known with main group metals. Especially the trispyrazolylboranate (scorpionate) complexes of the heavy alkaline earth metals show high thermal stability due to encapsulation of the metal ions by two tridentate ligands, precluding aggregation and ensuring volatility 16–20. In strontium bis[bis(di‐tert‐butylpyrazolyl)boranate], a boron–bound hydrogen atom acts as the third donor site, leading to a κ 3 ‐ N , N , H coordination of the anions 21,22.…”