Photoconductivity of Pentacene Thin Film Transistors

ABSTRACTA very large enhancement of the photoconductivity in pentacene transistors at negative gate voltages is observed. The enhancement is attributed to the separation of electron-hole pairs by the gate field and the consequent slow recombination. The ratio of photoconductivity to dark conductivity is approximately independent of mobility, for samples with a wide range of microstructure. The pentacene films were thermally deposited at different deposition rates and temperatures on silicon thermal oxide. The structure and the morphology of the films were studied by x-ray diffraction measurements and atomic force microscopy, and the influence of the deposition temperature on the morphology and structural properties is discussed. The size of the crystals is correlated with the crystalline bulk phase of the material, which increases with the deposition temperature and the film thickness. The mobility of the transistors increases with the size of the crystallites.

Download Full-text

Investigation Of Nucleation And Initial Stage Of Gan Growth By Atomic Force Microscopy And X-Ray Diffraction

MRS Proceedings ◽

10.1557/proc-482-93 ◽

1997 ◽

Vol 482 ◽

Cited By ~ 2

Author(s):

P. W. Yip ◽

S.-Q. Wang ◽

A. J. Drehman ◽

L. D. Zhu ◽

P. E. Norris

Keyword(s):

Atomic Force Microscopy ◽

Surface Morphology ◽

Deposition Temperature ◽

Yellow Luminescence ◽

X Ray Diffraction ◽

Rocking Curve ◽

X Ray ◽

Force Microscopy ◽

Atomic Force ◽

Initial Stage

AbstractThe nucleation and initial stage of GaN growth on sapphire was investigated by atomic force microscopy, X-ray diffraction and photoluminescence. A 15 to 30 nm thick GaN buffer layer deposited at proper conditions was extremely smooth and nearly amorphous. Proper post deposition annealing resulted in the buffer crystallized. The buffer layer deposition temperature, thickness and annealing time and temperature must be coordinated. Low deposition temperature and/or insufficient annealing of the buffer results in a GaN wafer which has fine spiking surface morphology with an RMS of 3.4 nm for 1.4 μm wafer, strong yellow luminescence and wide xray rocking curve FWHM. High deposition temperature, longer crystallization time, and a low growth rate results in a wafer which exhibits strong band edge luminescence without noticeable yellow luminescence, and a narrow (002) diffraction rocking curve. However, the surface morphology exhibits well developed hexagonal feature with RMS roughness of 14.3 nm for a 570 nm thick layer. X-ray rocking curve analysis revealed buffer crystallization, domain coalescence and alignment process. The FWHM of the ω–scan of GaN (101) diffraction was 1700–2000 arc seconds for 200–1400 nm wafers which indicates that the twist of the domains is not changing much with the growth.

Download Full-text

Investigation of the Effect of Uv-Assisted Oxidation and Nitridation of Hafnium Metal Films

MRS Proceedings ◽

10.1557/proc-780-y5.5 ◽

2003 ◽

Vol 780 ◽

Author(s):

C. Essary ◽

V. Craciun ◽

J. M. Howard ◽

R. K. Singh

Keyword(s):

Uv Radiation ◽

Photoelectron Spectroscopy ◽

Grazing Angle ◽

X Ray Diffraction ◽

Metal Thin Films ◽

X Ray ◽

Force Microscopy ◽

Si Substrates ◽

Atomic Force ◽

Silicon Interface

AbstractHf metal thin films were deposited on Si substrates using a pulsed laser deposition technique in vacuum and in ammonia ambients. The films were then oxidized at 400 °C in 300 Torr of O2. Half the samples were oxidized in the presence of ultraviolet (UV) radiation from a Hg lamp array. X-ray photoelectron spectroscopy, atomic force microscopy, and grazing angle X-ray diffraction were used to compare the crystallinity, roughness, and composition of the films. It has been found that UV radiation causes roughening of the films and also promotes crystallization at lower temperatures.Furthermore, increased silicon oxidation at the interface was noted with the UVirradiated samples and was shown to be in the form of a mixed layer using angle-resolved X-ray photoelectron spectroscopy. Incorporation of nitrogen into the film reduces the oxidation of the silicon interface.

Download Full-text

Low Molecular Weight Microfibers with Light Sensing Properties

Materiale Plastice ◽

10.37358/mp.17.4.4920 ◽

2017 ◽

Vol 54 (4) ◽

pp. 655-658

Author(s):

Andrei Bejan ◽

Dragos Peptanariu ◽

Bogdan Chiricuta ◽

Elena Bicu ◽

Dalila Belei

Keyword(s):

Molecular Weight ◽

Low Molecular Weight ◽

X Ray Diffraction ◽

Aromatic Rings ◽

X Ray ◽

Force Microscopy ◽

Light Sensing ◽

Sensing Applications ◽

Atomic Force ◽

Low Molecular Weight Compounds

Microfibers were obtained from organic low molecular weight compounds based on heteroaromatic and aromatic rings connected by aliphatic spacers. The obtaining of microfibers was proved by scanning electron microscopy. The deciphering of the mechanism of microfiber formation has been elucidated by X-ray diffraction, infrared spectroscopy, and atomic force microscopy measurements. By exciting with light of different wavelength, florescence microscopy revealed a specific optical response, recommending these materials for light sensing applications.

Download Full-text

Probing the Room Temperature Deuterium Absorption Kinetics in Nanoscale Magnesium Based Hydrogen Storage Multilayers Using Neutron Reflectometry, X-ray Diffraction, and Atomic Force Microscopy

The Journal of Physical Chemistry C ◽

10.1021/jp209296b ◽

2012 ◽

Vol 116 (9) ◽

pp. 5868-5880 ◽

Cited By ~ 15

Author(s):

W.P. Kalisvaart ◽

E.J. Luber ◽

E. Poirier ◽

C.T. Harrower ◽

A. Teichert ◽

...

Keyword(s):

Atomic Force Microscopy ◽

Hydrogen Storage ◽

Room Temperature ◽

Neutron Reflectometry ◽

Absorption Kinetics ◽

X Ray Diffraction ◽

X Ray ◽

Force Microscopy ◽

Atomic Force

Download Full-text

Nanocrystalline Solutions as Precursors to The Spray Deposition of Cdte Thin Films

MRS Proceedings ◽

10.1557/proc-382-461 ◽

1995 ◽

Vol 382 ◽

Cited By ~ 4

Author(s):

Martin Pehnt ◽

Douglas L. Schulz ◽

Calvin J. Curtis ◽

Helio R. Moutinho ◽

Amy Swartzlander ◽

...

Keyword(s):

Thin Films ◽

Atomic Force Microscopy ◽

Grain Size ◽

X Ray Diffraction ◽

X Ray ◽

Force Microscopy ◽

Cdte Nanoparticles ◽

Atomic Force ◽

Vis Spectroscopy ◽

Cdte Thin Films

ABSTRACTIn this article we report the first nanoparticle-derived route to smooth, dense, phase-pure CdTe thin films. Capped CdTe nanoparticles were prepared by injection of a mixture of Cd(CH3)2, (n-C8H17)3 PTe and (n-C8H17)3P into (n-C8H17)3PO at elevated temperatures. The resultant nanoparticles 32-45 Å in diameter were characterized by x-ray diffraction, UV-Vis spectroscopy, transmission electron microscopy, thermogravimetric analysis and energy dispersive x-ray spectroscopy. CdTe thin film deposition was accomplished by dissolving CdTe nanoparticles in butanol and then spraying the solution onto SnO2-coated glass substrates at variable susceptor temperatures. Smooth and dense CdTe thin films were obtained using growth temperatures approximately 200 °C less than conventional spray pyrolysis approaches. CdTe films were characterized by x-ray diffraction, UV-Vis spectroscopy, atomic force microscopy, and Auger electron spectroscopy. An increase in crystallinity and average grain size as determined by x-ray diffraction was noted as growth temperature was increased from 240 to 300 °C. This temperature dependence of film grain size was further confirmed by atomic force microscopy with no remnant nanocrystalline morphological features detected. UV-Vis characterization of the CdTe thin films revealed a gradual decrease of the band gap (i.e., elimination of nanocrystalline CdTe phase) as the growth temperature was increased with bulk CdTe optical properties observed for films grown at 300 °C.

Download Full-text

Frequency and Temperature Dependence of Dielectric Properties of Orthorhombic HoMnO3 Thin Films

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1025-1026.427 ◽

2014 ◽

Vol 1025-1026 ◽

pp. 427-431

Author(s):

Ping Gao ◽

Wei Zhang ◽

Wei Tian Wang

Keyword(s):

Dielectric Properties ◽

Pulsed Laser ◽

Signal Amplitude ◽

Debye Model ◽

Laser Deposition ◽

X Ray Diffraction ◽

X Ray ◽

Force Microscopy ◽

Atomic Force ◽

Cole Diagram

Orthorhombic HoMnO3 films were prepared epitaxially on Nb-doped SrTiO3 single crystal substrates by using pulsed laser deposition technique. The films showed perfectly a-axis crystallographic orientations. X-ray diffraction and atomic force microscopy were used to characterize the films. The complex dielectric properties were measured as functions of frequency (40 Hz~1 MHz) and temperature (80 K~300 K) with a signal amplitude of 50 mv. The respective dielectric relaxation peaks shifted to higher frequency as the measuring temperature increased, with the same development of real part of the complex permittivity. The cole-cole diagram was obtained according to the Debye model, and the effects of relaxation process were discussed.

Download Full-text

Lateral Size of Self-Patterned Nanostructures Controlled by Multi-Step Deposition

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.106.117 ◽

2005 ◽

Vol 106 ◽

pp. 117-122 ◽

Cited By ~ 3

Author(s):

Izabela Szafraniak ◽

Dietrich Hesse ◽

Marin Alexe

Keyword(s):

Electron Microscopy ◽

Ultrathin Films ◽

Lateral Size ◽

X Ray Diffraction ◽

X Ray ◽

Force Microscopy ◽

Atomic Force ◽

Non Volatile Memory ◽

Ferroelectric Capacitors ◽

Scanning Electron

Self-patterning presents an appealing alternative to lithography for the production of arrays of nanoscale ferroelectric capacitors for use in high density non-volatile memory devices. Recently a self-patterning method, based on the use of the instability of ultrathin films during hightemperature treatments, was used to fabricate nanosized ferroelectrics. This paper reports the use of the method for the preparation of PZT nanoislands on different single crystalline substrates - SrTiO3, MgO and LaAlO3. Moreover, a multi-step deposition procedure in order to control lateral the dimension of the crystals was introduced. The nanostructures obtained were studied by atomic force microscopy, scanning electron microscopy and X-ray diffraction.

Download Full-text

Studies of Nanomechanical Properties of Pulsed Laser Deposited NbN films on Si Using Nanoindentation

MRS Proceedings ◽

10.1557/opl.2012.152 ◽

2012 ◽

Vol 1424 ◽

Author(s):

M. A. Mamun ◽

A. H. Farha ◽

Y. Ufuktepe ◽

H. E. Elsayed-Ali ◽

A. A. Elmustafa

Keyword(s):

Thin Films ◽

Pulsed Laser ◽

Niobium Nitride ◽

X Ray Diffraction ◽

Si Substrate ◽

Force Microscopy ◽

Atomic Force ◽

Wide Range ◽

Pile Up ◽

Average Modulus

ABSTRACTNanomechanical and structural properties of pulsed laser deposited niobium nitride thin films were investigated using X-ray diffraction, atomic force microscopy, and nanoindentation. NbN film reveals cubic δ-NbN structure with the corresponding diffraction peaks from the (111), (200), and (220) planes. The NbN thin films depict highly granular structure, with a wide range of grain sizes that range from 15-40 nm with an average surface roughness of 6 nm. The average modulus of the film is 420±60 GPa, whereas for the substrate the average modulus is 180 GPa, which is considered higher than the average modulus for Si reported in the literature due to pile-up. The hardness of the film increases from an average of 12 GPa for deep indents (Si substrate) measured using XP CSM and load control (LC) modes to an average of 25 GPa measured using the DCM II head in CSM and LC modules. The average hardness of the Si substrate is 12 GPa.

Download Full-text