Composition, morphology and particle size control in nanocrystalline iron oxide films grown by single-source CVD

Mathur, Sanjay; Veith, Michael; Sivakov, Vladimir; Shen, Hao; Gao, Hongze

doi:10.1051/jp4:2001362

Cited by 11 publications

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“…The observed discrepancy in the mass loss in the 8 ] was studied in a horizontal, cold-wall, glass reactor, working under reduced pressure. [28] A series of thin films were deposited onto inductively heated silicon substrates (450± 600 C) resting on a graphite susceptor. The substrate temperature was monitored using a thermocouple connected to the high frequency controller.…”

Section: Thermogravimetry and Differential Thermal Analysis (Tg/dta)mentioning

confidence: 99%

Chemical Vapor Growth of NiGa2O4 Films: Advantages and Limitations of a Single Molecular Source

Mathur¹,

Barth²,

Shen³

2005

Chem. Vap. Deposition

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8 ] is susceptible to the distance and geometry of the effective diffusion path. Investigations on CVD deposits obtained using different transport pathways (reservoir ® substrate) show that gas-phase travel through a long (39 cm) and angular reactor tube induces fragmentation of the heterometal compound, which yields minor amounts of Ni, NiO, and Ga 2 O 3 (amorphous), besides the target (NiGa 2 O 4 ) composition. Shortened reservoir ® substrate path length (13 cm) produced stoichiometric NiGa 2 O 4 films, apparently due to reduced collision probabilities and a laminar flow. In both cases, the chemical composition was determined using energy-dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS), whilst the structure was evaluated using powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). From these, the advantages and limitations of the single molecular source in the growth of NiGa 2 O 4 films could be determined.

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Section: Thermogravimetry and Differential Thermal Analysis (Tg/dta)mentioning

confidence: 99%

Chemical Vapor Growth of NiGa2O4 Films: Advantages and Limitations of a Single Molecular Source

Mathur¹,

Barth²,

Shen³

2005

Chem. Vap. Deposition

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“…1). In an independent study, Mathur et al, [38] and Graetz, [39] have carried out the structural analysis of iron tert-butoxide. The results obtained in both cases confirm the dimeric structure.…”

Section: Synthesis and Characterization Of The Precursormentioning

confidence: 99%

“…Since the main source of carbon in the metal±organic (MO) CVD is the entrapment of organic rests and incompletely decomposed precursor molecules during the film growth, the low contamination level in the film exhibits the clean ligand stripping mechanism operative in the thermolysis of [Fe-(O t Bu) 3 ] 2 . [38,39] The thermally activated fragmentation of metal tert-butoxides generally produce tert-butyl alcohol, iso-butylene, and dihydrogen (Eq. 2) [42] as volatile by-products that can be easily removed from the deposition zone to obtain oxides with minimum carbon contamination.…”

Section: Cvdmentioning

confidence: 99%

“…The observed morphological features are typical of hematite and magnetite films obtained by MOCVD. [38] The hematite films were obtained by performing the CVD at 400 C (as well as by annealing the magnetite films in air at 450 C), a fact borne out by the XRD and XPS data. However, the morphology of the hematite crystals was found to be different in the two cases; the hematite particles formed directly from the decomposition of [Fe(Ot Bu) 3 ] 2 exhibit a spindle-like morphology whereas spherical grains are obtained from the oxidation (by air) of magnetite films (Figs.…”

Section: Scanning Electron Microscopymentioning

confidence: 99%

“…In addition, the steric profile of tert-butoxide group hinders oligomerization through alkoxy bridging thereby imparting sufficient volatility for the CVD process. 2 , was obtained from a salt elimination reaction between anhydrous FeCl 3 and three equivalents of NaO t Bu in tetrahydrofuran (THF), [38,39] as shown in Equation 1.…”

Section: Introductionmentioning

confidence: 99%

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Phase-Selective Deposition and Microstructure Control in Iron Oxide Films Obtained by Single-Source CVD

Mathur¹,

Veith²,

Sivakov

et al. 2002

Chem. Vap. Deposition

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Iron(III) tert-butoxide, [Fe(O t Bu) 3 ] 2 , was used as a single source for iron and oxygen to obtain nanocrystalline hematite (Fe 2 O 3 ) or magnetite (Fe 3 O 4 ) films by low-pressure (LP) CVD. The decomposition profile of the molecular precursor and the crystallization temperature of iron oxide were derived from thermogravimetry/differential thermal analysis (TG/DTA). The substrate temperature was found to markedly influence the morphology and Fe/O stoichiometry in the deposited films. The morphological features and phase identification of the grown films were obtained by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The compositional identity of the phases was determined by the X-ray photoelectron spectroscopy (XPS) of the CVD deposits. Annealing the films ex-situ under reducing or oxidizing conditions allows selective interconversion (Fe 2 O 3 « Fe 3 O 4 ) among the deposited phases with no particle size variation. The interplay between the rate of precursor delivery and substrate temperature controlled the mean particle size in the films. Magnetite film with a mean particle size of 10 nm was obtained on silicon at 450 C. Formation of larger grains and grain clusters was observed at higher temperatures. High coercivity (4000 Oe) and small saturation magnetization (0.3 emu g ±1 ) of the Fe 3 O 4 film confirmed superparamagnetic behavior due to small particle size. Absorption spectra of magnetite and hematite films deposited on glass show them to be transparent to the visible light. The sheet resistance of nanocrystalline Fe 3 O 4 and Fe 2 O 3 films was found to be 2.4 kX and 2 MX, respectively.

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Thermal hysteresis of spin reorientation at Morin transition in alkoxide derived hematite nanoparticles

et al. 2004

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We present results on structural and magnetic properties of highly crystalline α-Fe 2 O 3 nanoparticles of average size ~200 nm, synthesized from a novel sol-gel method using metal alkoxide precursor. These particles are multi-domain, showing the weak ferromagnetic-antiferromagnetic (WF-AF) transition (i.e., the Morin transition) at T M = 256(2) K. Mössbauer measurements revealed a jump in hyperfine parameters (HP's) at T ~ T M , which also displays thermal hysteresis upon cooling or heating the sample. The analysis of HP's as a function of temperature allowed us to discard temperature gradients as well as the coexistence of WF/AF phases as possible origins of this hysteretic behaviour. Instead, the hysteresis can be qualitatively explained by the small size and high-crystallinity of the particles, which hinder the nucleation of the WF or AF phases yielding metastable states beyond T M .

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Composition, morphology and particle size control in nanocrystalline iron oxide films grown by single-source CVD

Cited by 11 publications

References 0 publications

Chemical Vapor Growth of NiGa2O4 Films: Advantages and Limitations of a Single Molecular Source

Chemical Vapor Growth of NiGa2O4 Films: Advantages and Limitations of a Single Molecular Source

Phase-Selective Deposition and Microstructure Control in Iron Oxide Films Obtained by Single-Source CVD

Thermal hysteresis of spin reorientation at Morin transition in alkoxide derived hematite nanoparticles

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