ERBIUM β-DIKETONATES

Erbium tris( 2,4-pentanedionate) Er(acac)3

Er(acac)3 was reported to be prone for oligomerization, which results in progressively diminishing vapour pressure, presenting a serious disadvantage for using it as the erbium precursor for classical thermal CVD.

Er(acac)3 for Er-doped Al2O3 by aerosol CVD

     Erbium tris( 2,4-pentanedionate) Er(acac)3 (combined with Al(acac)3 as Al source), both dissolved in an organic solvent,  was applied as erbium precursor for the growth of Er-doped Al2O3 dielectric films at 573-813 K (300-540°C) by atmospheric pressure aerosol CVD. Amorphous, transparent, pure Er-doped alumina films were deposited for potential applications as amplifying media for integrated optics. The decreasing the deposition temperature resulted in the increase of the Er doping concentration, and decrease of the  refractive index (1.61 at 813 K (540°C) to 1.53 at 573 K (300°C)). [i]

[i] J.L Deschanvres, W Meffre, J.C Joubert, J.P Senateur, F Robaut, J.E Broquin, R Rimet, J. Alloys and Compounds, 1998, vol. 275–277, p.742–745, « Rare earth-doped alumina thin films deposited by liquid source CVD processes »

Erbium tris(acetylacetonate) 1,10-phenantroline adduct Er(acac)3(phen)

Er(acac)3(phen) for Er2O3 by low-pressure MOCVD

    Erbium tris(2,4-pentanedionate) 1,10-phenantroline adduct (or Erbium tris(acetylacetonate) 1,10-phenantroline adduct)  Er(acac)3(phen) was applied  as  precursor for the growth of Er2O3 films on Si(100) substrates by low-pressure MOCVD, which allows deposition of high quality layers at relatively low growth temperatures. Er(acac)3(phen) was sublimed at 200 °C (unlike unadducted Er(acac)3, this adduct is stable against oligomerization, and thus has significantly more stable vapor pressure). Erbia layers were deposited at temperatures from 450 to 600 °C, total pressure 2-100 Torr, 30 sccm Ar as  carrier gas and 100 sccm O2 as oxidant. The structural and electrical properties of deposited Er2O3 films were studied; the obtained layer thickness was 100-700 nm (by stylus profilometry and cross-sectional SEM). Er2O3 layers grown at lower temperatures were smooth, but poorly crystalline, whereas erbia films grown at higher temperatures were polycrystalline. The deposited Er2O3 layers had a dielectric constant in the range 8–20, and were achieving a minimum total fixed oxide charge density (Nf) of -1×1010 cm-2 and a minimum 10 mV hysteresis in the bidirectional capacitance–voltage characteristics.[i] ,[ii]

     The microstructure, crystallinity, and physical properties of Er2O3 layers grown by MOCVD using Er(acac)3(phen) precursor  were investigated. The as grown Er2O3films were polycrystalline. Incorporation of heteroatomic species (like C impurity) into the layers was dependent on the film's growth conditions. The obtained Er2O3 layers had 5.8 eV bandgap, but . the as-grown films were leaky; thin and thick Er2O3films displayed similar properties this it is possible to scale down these films for potential uses as dielectric layers. [iii]

 [i] M.P. Singh, C.S. Thakur; K. Shalini; N. Bhat, S.A.Shivashankar, Appl. Phys. Lett., 2003, Vol.83, Iss.14, p. 2889 - 2891, « Structural and electrical characterization of erbium oxide films grown on Si(100) by low-pressure metalorganic chemical vapor deposition », http://eprints.iisc.ernet.in/2761/1/vapor_deposition.pdf

[ii] MP Singh, CS Thakur, K Shalini, N Bhat, S.A. Shivashankar,  Electrochem Soc. Proc. 2003, p.358-366

https://electrochem.org/dl/ma/203/pdfs/0385.pdf , « Characterization of a potential gate dielectric: MOCVD-grown erbium oxide on silicon »

[iii]  M.P. Singh, T. Shripathi,  K. Shalini,  S.A. Shivashankar,  Materials Chemistry and Physics, 2007, vol. 105, Iss. 2–3, p. 433–441 , « Low pressure MOCVD of Er2O3 and Gd2O3 films »,     http://dx.doi.org/10.1016/j.matchemphys.2007.05.009

Erbium tris(2,2,6,6,-tetramethyl-3,5-heptanedionate) Er(thd)3

    Erbium tris(2,2,6,6,-tetramethyl-3,5-heptanedionate) Er(thd)3 was studied by simultaneous electron diffraction and mass spectroscopic study in the gasphase; it was determined that Er(thd)3 saturated vapor at 136(5)°C consists solely of molecules. D3 symmetry was found to be preferable for free Er(thd)3 molecules, according to electron diffraction data; the ErO6 coordination polyhedron has a structure close to an antiprism.[i]

[i] N. I. Giricheva, N. V. Belova, G. V. Girichev, N. V. Tverdova, S. A. Shlykov, N. P. Kuzmina, I. G. Zaitseva, J. Struct. Chemistry, 2003, vol.44, iss. 5, pp. 771-778, « Structure and Energetics of β-Diketonates. XII. Structure of Lanthanide tris -Dipivaloylmethanates for Er(thd)3 Used as an Example » 

Er(thd)3 for Er-doped GaN by MOCVD

    Er(thd)3 has been applied as a precursor for the growth of Er-doped GaN films by MOCVD. However, the doping efficiency was limited by high transport temperatures. [4]

Er(thd)3 for Er-doped ZnO by AACVD

     Erbium tris(2,2,6,6-tetramethyl-3,5-heptadionate) (Er(thd)3) was applied as erbium precursor (with zinc acetates dihydrate Zn(OAc)2·2H2O) as Zn source) for deposition of Er-doped ZnO layers by aerosol assisted chemical vapor deposition (AACVD) on Si (1 1 1) substrate at 370–500 °C temperatures. The morphology of the as-deposited films was dependent on the substrate temperature; nano-disk shaped grains were grown on the top of layer surface. Strongly c-axis oriented hexagonal wurtzite structure ZnO:Er films without any second phase were obtained after annealing in air atmosphere, according to XRD. For optimum ZnO:Er concentration, erbium ions were found to occupy C4v site symmetry in the pseudo-octahedral structure. Intense and well resolved luminescence spectra were obtained for 2.5 at.% Er doped ZnO films under 488 nm excitation, the intra 4f–4f green emission (2H11/2, 4S3/2 → 4I15/2 transitions) gradually increased with increasing annealing temperature. However, using 325 nm excitation, all ZnO:Er samples showed ~ 380 nm UV emission originating from a near band-edge emission,  and a broad band green emission (~520 nm) from deep levels; the optical response correlated with crystallinity of the layers.[[i]]

[i] R.Elleuch, R. Salhi, N. Maalej, J.-L. Deschanvres, R. Maale, Mater. Sci. Eng.: B, 2013, Vol.178, iss.17, p.1124–1129, « Structural and luminescence correlation of annealed Er-ZnO/Si thin films deposited by AACVD process »

Er(thd)3 for Er2O3 by ALD

      Er(thd)3 and ozone O3 as oxidant have been applied for the preparation of cubic Er2O3 films by ALD; the region of constant growth rate for Er2O3 (ALD window) was observed at 250–375°C on Si(100) (growth rate 0.25 Å/cycle), and 275–350 °C on soda lime glass substrates (growth rate 0.20 Å/cycle). Polycrystalline cubic-phase Er2O3 layers were obtained, with preferred orientation changing from (4 0 0) to (2 2 2) when the growth temperature was raised >325 °C; whereas films grown <250 °C were amorphous. Er2O3 layers deposited within the ALD window were very smooth (rms=0.3–1.4 nm by AFM). The grown films were nearly stoichiometric Er2O3 with some H (1.7–4.0 at.%), C (0.5–1.8 at.%) and F (0.7–1.7 at.%) impurities, as was determined by TOF-ERD.[i]

[i] J. Päiväsaari, M. Putkonen, T. Sajavaara, L. Niinistö, J. Alloys Compounds, 2004, vol 374, p.124-128, « Atomic layer deposition of rare earth oxides: erbium oxide thin films from β-diketonate and ozone precursors »

Er(thd)3 for ErxGa2-xO3 by ALD

    Er(thd)3, together with Ga(acac)3 and O3 as co-reactants, was applied for the growth of ErxGa2-xO3 (0 ≤ x ≤ 2) thin films by ALD at 350°C. Growth rate was 0.25-0.28Å/cycle), films impurities level was (C, H, N <0.2-0.3at.%, F 0.6-2.2at.%). The effective permittivity of the films was 10-11.3. As deposited films were amorphous but upon annealing at 900-1000 °C under N2 atmosphere they crystallized to Er3Ga5O12 or to a mixture β-Ga2O3 + Er3Ga5O12. Film rms surface roughnesses was <1.0 nm by AFM regardless of film composition. [469] The comparison of this precursor system with erbium-cyclopentadienyl containing one is presented below.

Erbium tris(2,2,6,6,-tetramethyl-3,5-heptanedionate) tetraglyme adduct [Er(thd)3]2(tetraglyme)

Fig. . Molecular structure of [Er2(thd)6(tetraglyme)].

      Erbium tris(2,2,6,6,-tetramethyl-3,5-heptanedionate) tetraglyme adduct [{Er(tmhd)3}2tetraglyme)], a volatile erbium(III) β-diketonate compound symmetrically bridged by tetraglyme, was synthesized and characterized. [{Er(tmhd)3}2tetraglyme)],  sublimes almost quantitatively (155-170°C at 10-3 Torr); TGA demonstrated sublimation of over 95% of all material between 130 and 295°C, with only ~3% residue by 600°C. For comparison, the hydrated species Er(tmhd)3(H2O) gave a weight loss of only ca 3% by 110°C (due to loss of the water), followed by sublimation of the majority of material at 190-315°C, leaving a residue of 4.5% by 600°C. The crystal structure of [Er(tmhd)3]2(tetraglyme) was determined by single crystal XRD; it revealed two Er(tmhd)3 moieties linked by a bridging tetraglyme molecule, with Er atoms have distorted squareantiprismatic geometries. The mass spectroscopy supported the structure determined by XRD: the major species was [Er(tmhd)2(tetraglyme)] +.

From the above results, it was suggested that [{Er(tmhd)3}2tetraglyme)] could be promising as CVD precursor for Er-containing layers, because of it volatility supported by saturation of the metal coordination sphere and thus reducing the possibility of oligomerization processes. [[i]]

[i] A. Darr, D. Michael, P. Mingos, D. E. Hibbs, M. B. Hursthouse, K.M. Abdul Malik, Polyhedron, Vol.15, Iss. 1996, p.3225–3231, https://www.sciencedirect.com/science/article/pii/0277538796000113

Erbium tris(2,2,6,6,-tetramethyl-3,5-octanedionate) [Er(tmod)3], Erbium tris(2,2,6,6,-tetramethyl-3,5-octanedionate) tetraglyme adduct [Er(tmod)3](tetraglyme)

Fig. . TGA-DTA curves for Er(tmod)3(tetraglyme)

 Erbium tris(2,2,6,6,-tetramethyl-3,5-octanedionate) Er(tmod)3 and its tetraglyme adduct with Er(tmod)3(tetraglyme) were compared as potential erbium MOCVD precursors. The thermal properties of both complexes were studied by using thermogravimetric (“TG-DTA) analysis. The unadducted Er(tmod)3 is solid, whereas the adducted molecule Er(tmod)3(tetraglyme) is liquid and leaves no residue after full evaporation (which finishes at ca. 330°C). The TGA-DTA curves for Er(tmod)3(tetraglyme) are shown in Fig. [i]

[i] C Dussarrat, US Patent App. 12/536,804, 2009 , « NOVEL LANTHANIDE BETA-DIKETONATE PRECURSORS FOR LANTHANIDE THIN FILM DEPOSITION »

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