Chromium bis(cyclopentadienyl) Cr(η5-C5H5)2
(chromocene CrCp2)
Chromium (II) cyclopentadienyl Cr(η5-C5H5)2 is a sublimable solid with meting point 168-170°C.
Chromocene has been synthesized by metathesis reaction between chromium dichloride and sodium cyclopentadienyl:
CrCl2 + 2 Na(C5H5) → Cr(η5-C5H5)2 + 2 NaCl
Its crystal and molecular structure was determined by a low-temperature single-crystal X-ray diffraction study; the average Cr-C bond length is 2.151(13) Å. [947]
CrCp2 for Cr carbides CVD
Chromocene has been employed as precursor for the hot-wall low-pressure CVD growth of chromium carbide films. Attempts to grow films at 500°C were unsuccessful , but upon stepwise increase of the temperature up to 630°C carbide films were obtained.The morphology of this coating was different from that obtained in similar conditions for chromium (0) diarenes (Cr(C6H6)2 and Cr(C6H5iPr)2) (Fig. ): the film appeared as a tangle of starfishlike ~1 µm size crystallites. According to XRD, a mixture of 3 chromium carbides (Cr7C3, Cr23C6, Cr3C2) was present in the layer; in total film contained 9.8 wt.% C, lower than that with other precursors. The binding energies (XPS) of Cr 2p3/2 at 574.8 eV and C is at 283.3 eV correlated well with a chromium carbide. The existence of graphitic carbon was revealed by the shoulder on the high binding energy side of the C 1s level (285.1 eV) ; the free carbon ratio (34%) was close to the values found in chromium carbide films grown from the other precursors, despite higher growth temperature).[948]
Cr(η5-C5H5)2 for Cr doping of InGaAs/InP by CVD
High-quality Cr-doped InGaAs/InP(001) MQWs have been grown by MOVPE using CrCp2 as chromium precursor. Dopant concentrations were measured by SIMS, the structural characterization was performed by HR XRD. Chromium doping increases carrier recombination rate upon an increase of defect density, the electronic and structural properties are essentially preserved, according to frequency- and time-resolved optical spectroscopy of the MWQ ground-state transition. [949]
Cr(η5-C5H5)2 for Cr doping of GaN by CVD
CrCp2 was applied as precursor for the MOVPE growth of Cr-doped GaN layers for spintronics applications (Cr doping was predicted to produce the most stable ferromagnetic state in transition metal doped GaN). Cr concentrations in solid phase up to 2·1019 at/cm-3 were achieved according to SIMS. The influence of precursors supply, carrier gas type and growth temperature on Cr incorporation efficiency in the GaN layers was studied. The incorporated Cr in solid phase was linearly dependent on the mole fraction of Cp2Cr in gas phase. Surface morphology, structural and optical properties were measured by SEM, AFM, XRD and PL. Best GaN:Cr structural and morphological propeties was obtained at Tdep 950 °C (where highest Cr conc. was achieved), while fior undoped GaN optimum growth temperature 1125°C. Cr-doped GaN layers had remanent magnetization even above RT according to SQUID zero field heating. [950, 951, 952]
Cr(η5-C5H5)2 for Cr doping of B5C by CVD
Chromocene was reported to be applied precursor for the preparation of Cr-doped B5C layers by CVD (to increase their n-type conductivity) [953]
Chromium bis(ethylcyclopentadienyl) Cr(η5-EtC5H4)2
Chromium bis(ethylcyclopentadienyl) Cr(EtCp)2 has been proposed as potetial ALD precursor for growth of chromium oxides.[954]
Chromium bis(isopropylcyclopentadienyl) Cr(η5-iPrC5H4)2
Chromium bis(isopropylcyclopentadienyl) Cr(iPrCp)2 has been considered as potential precursor for the growth of Cr metal by CVD []
Chromium bis(pentamethylcyclopentadienyl) Cr(η5-C5Me5)2 (dekamethylchromocene Cr(Me5Cp)2)
Chromium bis(pentamethylcyclopentadienyl) Cr(η5-C5Me5)2 has been suggested as potential precursor for ALD of Cr2O3 thin films, however, no examples were given [957]