Roberta G. Toro

Dielectric properties of Pr2O3 high-k films grown by metalorganic chemical vapor deposition on silicon

Praseodymium oxide (Pr2O3) thin films have been deposited on Si(100) substrates by metalorganic chemical vapor deposition using praseodymium tris-2,2,6,6-tetramethyl-3,5-heptandionate as source material. Film structural, morphological, and compositional characterizations have been carried out. Dielectric properties have been studied as well by capacitance–voltage and current–voltage measurements on metal-oxide-semiconductor capacitors of several areas. The Pr2O3 films have shown a dielectric constant e=23–25 and a leakage current density of 8.8×10−8 A/cm2 at +1 V.

Morphological and structural control of nanostructured oriented CeO2 films grown on random metallic substrates

CeO2 (cubic fluorite) thin films have been deposited on no-rolled Hastelloy C276 substrates by metal-organic chemical vapour deposition (MOCVD) from the Ce(hfa)3·diglyme [Hhfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedione; diglyme = (CH3O(CH2CH2O)2CH3)] precursor. The X-ray patterns of all samples grown in the 350–550 °C temperature range point to the formation of oriented CeO2 films, while at higher deposition temperatures (650–850 °C) random CeO2 films are formed. XRD data indicate that 450 °C is the best deposition temperature. Detailed studies of the influence of all deposition parameters (precursor vaporization temperature, O2 and Ar gas flows, deposition temperature and time) on the CeO2 film growth have been carried out. There is evidence that the deposition process occurs in a mass transport regime. A suitable rationale for the observed textural changes vs. temperature has been proposed and the present columnar grain morphology, depending upon deposition temperatures, has been related to the zone model proposed by Mochvan and Demchishin for physical vapour deposition processes.

Breakdown kinetics of Pr2O3 films by conductive-atomic force microscopy

The dielectric breakdown (BD) kinetics of praseodymium thin films has been determined by comparison between current-voltage measurements on large-area (up to 78.54μm2) metal-oxide-semiconductor structures and conductive-atomic force microscopy (C-AFM). C-AFM clearly images the weak BD single spots under constant voltage stresses. The stress time on the single C-AFM tip dot was varied from 2.5×10−3 to 8×10−2s. The density of BD spots, upon increasing the stress time, exhibits an exponential trend. The Weibull slope and the characteristic time of the dielectric BD have been determined by direct measurements at nanometer scale.

Study of the Thermal Properties of Pr(III) Precursors and Their Implementation in the MOCVD Growth of Praseodymium Oxide Films

A praseodymium adduct, Pr(hfa) 3 .diglyme [(H-hfa = 1,1,1,5,5,5-hexafluoro-2,4-pentandione, diglyme = CH 3 O(CH 2 CH 2 O) 2 CH 3 )] has been synthesized. It has been applied as a Pr source for the metallorganic chemical vapor deposition (MOCVD) of praseodymium containing films on silicon substrate and compared with Pr(tmhd) 3 [(H-tmhd = 2,2,6,6-tetramethyl-3,5-heptandione)] precursor. Physical and thermal properties of both Pr(hfa) 3 .diglyme and Pr(tmhd)3 precursors have been fully analyzed and their efficacy as MOCVD precursors for the growth of praseodymium oxide films have been fully tested. Depending on the oxygen partial pressure (p O2 ), different praseodymium oxide phases have been obtained.

From micro- to nanotransport properties in Pr2O3-based thin layers

In this paper, the conduction mechanisms in Si/SiO2/PrxSiyOz/Pr2O3/Au metal-insulator-semiconductor capacitors have been investigated. The dielectric stack has been produced by metal-organic chemical-vapor deposition. Nanoscopic and microscopic capacitance properties have been correlated. The capacitance-voltage (C-V) characteristics of 25-μm-radius metal-oxide-semiconductor capacitors have been evaluated and compared to the measurements performed by scanning capacitance microscopy (SCM). The study of the SCM images allows us to confirm the value of interface state density (Dit≈1012cm−2eV−1) obtained by C-V investigation excluding any defect or grain-boundary contribution in the capacitance phenomena. The conduction mechanisms have been investigated by current-density–voltage (J-V) measurements performed at different temperatures (from 100 to 200 °C). At low electric fields, a slight dependence of J-V characteristics in function of both temperature and electric field has been observed, while a relatively ...

Perovskite CaCu3Ti4O12 thin films for capacitive applications: From the growth to the nanoscopic imaging of the permittivity

The physical properties of CaCu3Ti4O12 (CCTO) thin films grown by metal organic chemical vapor deposition on LaAlO3 substrates have been investigated. The structural, compositional, and optical characteristics have been evaluated, and all the collected data demonstrated that in the obtained (001) epitaxial CCTO thin films, a low defect density is present. The electrical behavior of the deposited thin films has been studied from both micro- and nanoscopic points of view and compared with the properties reported in the literature. The electrical measurements on large area capacitors indicated that in the investigated work frequency range (102–106 Hz), the CCTO films possess dielectric constants close to the theoretically predicted “intrinsic” value and almost independent of the frequency. The nanoscopic dielectric investigation demonstrated that the deposited CCTO films possess n-type semiconducting nature and that a colossal extrinsic behavior can be locally achieved.

Nanoscale imaging of permittivity in giant-κ CaCu3Ti4O12 grains

The possibility to image the local permittivity in giant-κ dielectrics by scanning probe microscopy was demonstrated. In particular, the microstructure and the dielectric properties of CaCu3Ti4O12 (CCTO) films grown on (001) LaAlO3 substrates were studied. CCTO amorphous layers obtained by metal-organic chemical vapor deposition have been crystallized by subsequent rapid thermal treatments at 1100 °C. X-ray diffraction measurements demonstrated the growth of CCTO and CaTiO3 phases. As a novelty, large square CCTO grains (a few microns) were formed with a very high permittivity. The local impedance modulus, phase, and morphology were simultaneously acquired, and the local permittivity (around 8000 at 90 kHz) of each isolated CCTO grain was calculated.

Defects induced anomalous breakdown kinetics in Pr2O3 by micro- and nano-characterization

Praseodymium based dielectric thin films have been deposited by metal-organic chemical vapour deposition (MOCVD). The Weibull slope and the characteristic time of the dielectric breakdown (BD) have been determined at nanometer scale by conductive atomic force microscopy (C-AFM). An anomalous behaviour for the dielectric BD has been found. Its physical behaviour has been described taking into account the electrical properties investigated by nanoscopic measurements performed by scanning capacitance microscopy (SCM). Current density-voltage (J-V) measurements have been carried out at different temperatures (from 100 to 200 °C). At low electric fields, a slight dependence of J-V characteristics in function of both temperature and electric field has been observed, while a relatively strong dependence has been found at high fields. The calculation of the activation energies for conduction mechanisms in both field regions pointed out the presence of deep defects that play a relevant role in the BD kinetics.

MOCVD approach to perovskite based thin films: From high Tc superconductors to giant dielectric constant materials

Perovskite thin films with various functional properties have been synthesized through the Metal Organic Chemical Vapour Deposition (MOCVD). The MOCVD processes, used for the fabrication of a variety of advanced materials in thin film form, rely upon application of a molten multi-element source. The challenging in-situ strategy involves the use of a molten source consisting of a second-generation M(hfa)n•polyether (M = La, Ca, and Y; polyether = diglyme or tetraglyme) precursor which acts as a solvent for the other species. The approach is reported as a general route to the fabrication of multi-element oxides.

Electrical properties of MOCVD praseodymium oxide based MOS structures

Praseodymium oxide-based high k dielectric thin films grown by metal-organic chemical vapour deposition (MOCVD) at 750/spl deg/C on p-type Si (100) substrates have been proposed. It has been revealed by energy-filtered TEM analyses that depositions in 10/sup -3/ torr oxygen partial pressure produced a Pr/sub 2/O/sub 3/ and a Pr/sub n/O/sub 2n-2//spl middot/SiO/sub 2/ bottom layer. The electrical properties of both Pr/sub 2/O/sub 3//Pr/sub n/O/sub 2n-2//spl middot/SiO/sub 2/ structures and Pr/sub n/O/sub 2n-2//spl middot/SiO/sub 2/ thin layers have been investigated and compared.