Most usual out of tetrahalides for use as MOCVD/ALD precursor is tin tetrachloride SnCl4.
Synthesis:
Tin tetrachloride SnCl4 can be synthesized either (1) by chlorination of metallic tin, or by oxidation of tin dichloride by O2 in the presence of HCl.
Sn + 2 Cl2 → SnCl4
SnCl2 + 2 HCl + ½ O2 → SnCl4 + H2O
Vapor Pressure:
Tin tetrachloride SnCl4 has vapor pressure of 10 Torr ( 10 °C), 18.6 Torr ( 20 °C), 20 Torr ( 22 °C) [[i]]
In Arrenius form the vapor pressure dependence on temperature is following:
log10(P) = A’−(B’/(T+C’)) (P in bar, T in K) with A’ = 4,18162, B’ = 1384,537 und C’ = −54,377 in temperature region from 250,5 to 386 K (= - 23°C to 113°C) . [[ii]]
[i] (https://www.sigmaaldrich.com/catalog/product/aldrich/217913?lang=de®ion=DE)
[ii] https://de.wikipedia.org/wiki/Zinn(IV)-chlorid# ↑
(7. Stull, D.R.: Vapor Pressure of Pure Substances. Organic and Inorganic Compounds in Ind. Eng. Chem. 39 (1947) 517–540, doi:10.1021/ie50448a022.)
SnCl4 combined with Ge2H6 was applied as precursors for the epitaxial growth of GeSn layers (10 and 6.5 at.% Sn) on Si(100) at low growth temperatures
of 375°C and 400°C, respectively, by reduced pressure CVD using showerhead technology (AIXTRON) reactor.. The obtained GeSn layers had high crystalline quality. The growth kinetics in the low temperature
regime of 375oC to 500oC was studied; this regime is characterized by surface limited reactions. [[i]]
[i] Stephan Wirths, Dan Buca, A.T. Tiedemann, Bernhard Holländer, Patric Bernardy, Toma Stoica, Detlev Grützmacher and Siegfried Mantl, ECS Trans. 2013, vol. 50, iss. 9, 885-893 , doi: 10.1149/05009.0885ecst , http://ecst.ecsdl.org/content/50/9/885.short, « Epitaxial Growth of Ge1-xSnx by Reduced Pressure CVD Using SnCl4 and Ge2H6 »
GeH4 (with addition of SnCl4), was used as CVD precursor for the of high crystal quality fully strained and relaxed epitaxial Ge1-xSnx layers with Sn contents up to 12 at. % on Ge buffered Si substrates at temperatures <450°C in a commercial CVD reactor. Intrinsic, p-type, and n-type Ge1-xSnx
alloys were prepared, in which Sn was fully substitutional Applicability of grown GeSn alloy for light emitting and detecting devices was demonstrated by the growth of doped Ge/Ge1-xSnx/Ge heterostructures. Phosphorus doped Ge1-xSnx demonstrated photoluminescence
at wavelengths up to 2.4 μm [[i]]
[i] J. Margetis, S. A. Ghetmiri, W. Du, B. R Conley, A. Mosleh, R. Soref, G. Sun, L. Domulevicz, H. A Naseem, Sh.-Q. Yu, J. Tolle, ECS Trans. 2014, vol. 64, iss. 6, 711-720, doi: 10.1149/06406.0711ecst « Growth and Characterization of Epitaxial Ge1-XSnx Alloys and Heterostructures Using a Commercial CVD System »
SnCl4, combined with H2O or H2O2 as oxygen source, was applied for the preparation of transparent and conductive stannic oxide films by CVD at the low temperature (250°C); the prepared films were not doped with impurities. Films formed from with H2O as oxygen source, had superior electrical properties, compared to those grown using H2O2, despite lower deposition rate at the same deposition temperature. The SnCl4/ H2O system produced films with resistivities ~10–10-3 Ω cm (at 250-400°C growth temperatures), whereas SnCl4/ H2O system resulted in the films having with 102–10-2 Ω cm resistivities for the layers grown at 250 - 450°C. The variation in the electrical properties depended on the absorption of hydrogen peroxide, as well as on the grain size, which was dependent on the deposition temperature and the reaction system. The spectral transmissivity varied over the range 80–95% in the wavelength regions between 400 and 650 nm for 0.36–1.1 μm thick films for both reaction systems. [[i]]
SnCl4 combined with and H2O as oxygen source, were supplied separately in gas phase as precursors
for the deposition of SnO2 thin films on soda-lime glass substrates by atmospheric pressure CVD under various deposition conditions, which were numerically simulated using a commercial software package (assuming the main chemical reactions during deposition
followed Rideal–Eley mechanism) and compared to experimental observations; the estimated reaction activation energy was 79.3 kJ/mol and frequency factor—1.93 × 1010 m4/kmol·s. [[ii]]
[i] T. Muranoi, M. Furukoshi, Thin Solid Films, 1978, Vol. 48, Iss. 3, p. 309-318, https://doi.org/10.1016/0040-6090(78)90009-3, https://www.sciencedirect.com/science/article/pii/0040609078900093 « Properties of stannic oxide thin films produced from the SnCl4-H2O and SnCl4-H2O2 reaction systems »
[ii] J.-W. Park, B.-K. Kim, H. J. Kim, S. Park, Thin Solid Films, 2014, Vol. 550, p.114-120
https://doi.org/10.1016/j.tsf.2013.10.114, « Experimentation and simulation of tin oxide deposition on glass based on the SnCl4 hydrolysis in an in-line atmospheric pressure chemical vapor deposition reactor »
SnCl4 combined with O2 as oxidant was applied as precursor for the CVD growth of thin films of SnO2 on (100) surfaces of TiO2 (rutile) single crystals at 1100–1400°C, with N2 as carrier gas. The flow rate of SnCl4 varied from 0.08 to 2.7 ml/min, O2 flow was 1.5-19 ml/min. The growth experiments were carried out using N2 carrier gas for 0.5–40 h deposition time. The deposited layers consisted of SnO2 particles varying in shape from truncated bricks to ridgy hexagonal or rectangular grains, depending on the flow rate of SnCl4. Only when the flow rate of SnCl4 was low enough, SnO2 films crystallographic oriented as the rutile substrates were obtained. The large majority of the SnO2 grains in the layers were (100) oriented, however small amount of (101) oriented grains was present as well. [[i]]
[i] M. Nagano, J. Cryst. Growth, 1984, vol.69, Iss.2–3, p.465-468, https://doi.org/10.1016/0022-0248(84)90357-9, https://www.sciencedirect.com/science/article/pii/0022024884903579, « Chemical vapor deposition of SnO2 thin films on (100) surfaces of rutile single crystals »
SnCl4 (combined with TiCl4, and H2O), was applied as precursor for the growth of anatase type (SnxTi1−x)O2 solid solution layers, having compositions ranging from x=0 to 0.02, were grown by chemical vapor deposition (CVD). The (SnxTi1−x)O2 films were characterized by inductively coupled plasma (ICP) spectroscopy, XRD, SEM, EDX, HRTEM, and selected area electron diffraction (SAED). Lattice parameters were linearly dependent on the SnO2 content in the solid solution; the c / a ratio of the anatase structure increased with increasing the SnO2 content. The lattice parameters were not drastically infuenced by point defects of oxygen non-stoichiometry or Cl impurity. HRTEM or SAED did not reveal neither amorphous phases, nor ordered structures in the anatase type (Sn0.2Ti0.8)O2 solid solution crystals.[i]
[i] Byung-Chun Young , J. Cryst. Growth, 1992, Vol. 121, Iss. 1–2, Pages 148-154, https://doi.org/10.1016/0022-0248(92)90184-K, https://www.sciencedirect.com/science/article/pii/002202489290184K, « Characterization of anatase type (SnxTi1−x)O2 solid solutions grown by CVD »
Tin chloride SnCl4, combined with H2S as sulfur source, was reported to be useful as Sn precursor for the growth of SnS and SnS2 on glass substrates by atmospheric pressure
CVD, the method which can be directly integrated with commercial float glass manufacturing lines. The preparation of single-phase crystalline SnS2 films by APCVD was demonstrated. [[i]]
[i] L. S. Price, I. P. Parkin, Th. G. Hibbert, K.C. Molloy, Chem. Vapor Dep., Vol.4, Iss.6, 1998, p.222-225 Atmospheric Pressure CVD of SnS and SnS2 on Glass, https://onlinelibrary.wiley.com/doi/abs/10.1002/ (SICI)1521-3862(199812)04:06%3C222::AID-CVDE222%3E3.0.CO;2-6
Tin tetraiodide SnI4, combined with O2 as oxidant, was successfully applied as precursor for the growth SnO2 thin films by CVD at 350–700 °C temperatures on α-Al2O3(012) substrates; the conditions for epitaxial growth and deposition kinetics were studied. The growth rate was controlled by surface kinetics at temperatures 350-475 °C
and increased exponentially from 5 nm/h to 735 nm/h. Two different surface reactions are proposed: one involving SnI4 (at low growth temperatures), another involving SnI2 (at high temperatures). The SnO2 growth rate was controlled by mass transport
of the tin-containing species at high temperatures (> 475 °C). X-ray photoelectron spectroscopy (XPS) did not detect iodine contamination in the grown SnO2 layers. The layer growth epitaxial relationships followed the in-plane orientation relationships,
[010] SnO2∥[100] a-Al2O3 and [101] SnO2∥[121] a-Al2O3 . [[i]]
[i] J. Sundqvist, M. Ottosson, A. Hårsta, Chemical Vapor Deposition, Volume 10, Issue 2, pages 77–82, March, 2004 CVD of Epitaxial SnO2 Films by the SnI4/O2 Precursor Combination