Thermal chemistry of Mn2(CO)10 during deposition of thin manganese films on silicon oxide and on copper surfaces
(Color online) Mn 2 p (a), O 1s (b), and Si 2 p (c) x-ray photoelectron spectroscopy (XPS) data obtained after exposure of a native-SiO2/Si(100) surface to Mn2(CO)10 at the indicated temperatures. The experiments were carried out in the small homemade ALD reactor described in Sec. II by dosing 1 mTorr of the manganese precursor for 30 s. Self-limiting deposition is seen only between 445 and 465 K.
(Color online) Summary of the XPS data shown in Fig. 1 in terms of the coverages of the relevant species, estimated from the intensities of the corresponding XPS peaks. Submonolayer Mn-containing films with thicknesses of approximately 0.21 nm are deposited between 445 and 465 K, whereas multilayer growth resulting in films 1.7 and 3.8 nm in thickness is seen at 475 and 525 K, respectively.
(Color online) Mn 2p (a) and Si 2p (b) XPS signal intensities and manganese oxide film thicknesses (c) obtained after exposures of SiO2/Si(100) substrates to 1 mTorr of Mn2(CO)10 for 800 s. Data are shown for two temperatures (445 and 525) and for exposures of the surface to the Mn precursor alone (hatched blue bars) and in the presence of 200 Torr of H2 (solid red bars).
(Color online) Mn 2p (a), O 1s (b), and C 1s (c) XPS obtained after dosing a native-SiO2/Si(100) surface with Mn2(CO)10 at 625 K. The traces correspond to increasing exposures using pressures of approximately 5 × 10−7 (bottom four traces) or 5 × 10−6 (top three traces) Torr of the precursor in experiments carried out in the auxiliary chamber in the XPS analytical instrument (see Sec. II). In addition to increasing amounts of oxidized manganese, some carbidic carbon is deposited at high exposures.
(Color online) Summary of the XPS data shown in Fig. 4 in terms of the coverages of the relevant species, estimated from the intensities of the corresponding XPS peaks. There seems to be a small induction period in the uptake, after which thick films can be grown continuously with increasing exposures.
(Color online) Mn 2p XPS spectra from films grown on SiO2/Si(100) by exposing the surface to 7.5 × 10−5 Torr of Mn2(CO)10 for ∼1300 s. Data are shown for two temperatures: 425 (top trace) and 625 (bottom trace) K. Dots correspond to the raw data, and lines correspond to Gaussian fits to the different components, all riding on a Shirley background. Two peaks for the Mn 2p3/2 and Mn 2p1/2 components are provided for the manganese silicide (green solid lines; binding energies = 638.5 and 649.7 eV) and main (purple dashed lines; binding energies = 641.2 and 653.1 eV) and satellite (orange dotted lines; binding energies = 646.1 and 658.5 eV) contributions to either MnO (425 K trace) or MnSiO3 (625 K) signals. To be noted is the fact the low binding energy peaks assigned here to manganese silicide appear only at high temperatures (625 K).
(Color online) Depth profile Mn 2p XPS spectra obtained after a 150 000 L Mn2(CO)10 exposure at 625 K. Shown are traces for the SiO2/Si(100) surface right after the manganese deposition (bottom trace) and following three (middle trace) and nine (top trace) minutes of Ar+ sputtering. The low binding energy peaks, at 638.5 and 649.7 eV, grow relative to all the other features with increasing sputtering time, highlighting the fact that the manganese silicide layer is buried underneath the manganese silicate film.
(Color online) Mn 2p XPS spectra from experiments designed to test the mechanism of formation of the manganese silicate and manganese silicide films at low (425 K) and high (625 K) temperatures. (a) Traces for the film obtained by dosing 150000 L of Mn2(CO)10 at 425 K (bottom) and after annealing that film at 625 K (top). (b) Spectra for films made by first depositing 7500 L of Mn2(CO)10 at 425 K (bottom) and then adding another 15 000 L at 625 K (top). (c) Spectra for the films grown after first depositing 100 000 L of Mn2(CO)10 at 625 K (bottom) and then adding another 100 000 L at 425 K (bottom).
(Color online) Mn 2p (a), O 1s (b), and Si 2p (c) XPS from surfaces obtained by adsorbing 240 L of Mn2(CO)10 (4 × 10−6 Torr for 60 s) on either a native-SiO2/Si(100) (bottom set) or a copper (top set) substrate at 175 K and then heating to the indicated temperatures. The main transition seen in these data is that due to the decarbonylation of the original precursor around 225 K, evidenced by a shift in the Mn 2p peaks and by the disappearance of the O 1s and C 1s at 533.6 and 287.4 eV, respectively, associated with the carbonyl ligands.
List of samples reported in this study.
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