Atomic Layer Deposition of LaPO₄ and Ca:LaPO₄**

Abstract

Thin films of lanthanum phosphate (LaPO4) are produced by atomic layer deposition (ALD) for the first time, using a precursor combination of (CH3)3PO4, La(thd)3 (Hthd = 2,2,6,6‐tetramethylhepta‐3,5‐dione), H2O, and O3. The deposition process is studied via an in‐situ quartz crystal microbalance (QCM) and found to be a two‐step process in which both water and ozone contribute to the growth. The best results are obtained when both water and ozone are pulsed simultaneously. The growth is self‐limiting by nature, and a stoichiometric LaPO4 phase can be obtained for a 1:1 pulsed ratio of the two precursors. The resulting LaPO4 films are amorphous as deposited, and crystallize to the monoclinic structure after annealing in air for 10 h at 1350 °C. The LaPO4 thin films can also be doped by calcium during growth by replacing some of the La(thd)3 pulses by Ca(thd)2. Films where 4.4% of the lanthanum in LaPO4 is replaced by calcium are obtained.

Plasma-enhanced atomic layer deposition of vanadium phosphate as a lithium-ion battery electrode material

“…1 This comes at the expense of very slow growth (typically in the order of 1 Å /cycle), making ALD most suitable for very thin films. Although many different ALD processes have been developed for various classes of materials such as oxides, ii-vi and iii-v semiconductors, metal nitrides, metals, metal sulfides, and fluorides, 2 the existing reports on ALD of phosphates are still limited, [3][4][5][6][7][8][9][10][11][12][13] but have recently been increasing in number because of their relevance as electrode [14][15][16][17][18] or electrolyte [19][20][21][22] films in lithium-ion batteries.…”

Plasma-Enhanced Atomic Layer Deposition of Iron Phosphate as a Positive Electrode for 3D Lithium-Ion Microbatteries

“…Many ALD processes exist for various oxides, II-VI and III-V semiconductors, metal nitrides, metals, metal sulfides, and fluorides . ALD of phosphates is less common, but reported processes include aluminum phosphate, − calcium phosphate, titanium phosphate, , lanthanum phosphate, lithium phosphate, iron phosphate, , and lithium iron phosphate . An easy-to-use (and thus popular) phosphorus precursor is trimethyl phosphate (TMP); it is a cheap and stable liquid with a suitable vapor pressure.…”

Atomic Layer Deposition of Aluminum Phosphate Based on the Plasma Polymerization of Trimethyl Phosphate

“…Reports on the atomic layer deposition of phosphates are still scarce, but seem to be gaining popularity recently. Table presents a summary of the existing literature on this subject. − …”