Hae-Suk Jung

Structural and electrical properties of co-sputtered fluorinated amorphous carbon film

Fluorinated amorphous carbon (a-C:F) films were deposited by co-sputtering process using polytetrafluoroethylene and graphite targets. The deposition characteristics, bonding configuration, structure, and electrical properties of a-C:F films were investigated as a function of fluorine content in the range of 0–62 at.%. As the fluorine content increased, transformation of bonding configuration and micro-structure were observed. For the fluorine content below 22 at.%, fluorine in amorphous carbon did not significantly affect hybrid bonding configuration. However, with increasing fluorine content, CCFx and CF1 bonds were dominated and a further increase in fluorine content resulted in the formation of CF2 and CF3 bonds and then dielectric constant decreased from 10 to 2.7. Based on these results, correlations among bonds’ distribution, micro-structure and dielectric property of a-C:F films were established.

The structural and electron field emission characteristics of pulsed laser deposited diamond-like carbon films with thermal treatment

Abstract Diamond-like carbon (DLC) films have been deposited on Si(100) by pulsed laser deposition (PLD) using 355 nm (Nd:YAG) laser. In order to investigate the factor that dominates the electron field emission behavior of DLC film, structural and electrical properties have been studied as a function of anneal temperature. Degradation of DLC film properties began to be observed above 400°C but, in case of plasmon energy loss and emission behavior, there were variations of properties at 300°C. From these results, we are convinced that anneal treatment modifies sp3/sp2 bonding ratio in surface as well as bulk of film but the anneal effect is more intensified on the surface than the bulk of DLC film. It is also observed that the electron field emission property is affected by the modification of sp3/sp2 bonding ratio in the film surface.

Enhancement of sp3 hybridized C in amorphous carbon films by Ar ion bombardment and Si incorporation

We report an effective method of increasing the sp3 hybridization fraction in sputtered amorphous carbon (a-C) film by the combination of Ar ion bombardment and Si incorporation. In the deposition of an a-C film, Ar ion bombardment by controlling the applied bias voltage plays a role in creating high stress in film and causes the local bonding configuration to change to a sp3 hybridized bond. Simultaneously, the incorporated Si in an a-C network breaks the sp2 hybridized bonded ring and promotes the formation of a sp3 hybridized bond. This enhancement of the sp3 hybridized bonding characteristic is maximized for an a-C film with 23 at. % of Si and 100–150 V of applied bias voltage. In this region, the increase of resistivity, optical band gap, and mechanical hardness of a-C is attributed to the reduction of the sp2 hybridized bonded ring and increased fraction of the sp3 hybridized bond. However, at a higher bias voltage above 150 V, the enhancement effect is reduced due to the resputtering and thermally ...

Fabrication and characterization of diamond-like carbon thin films by pulsed laser deposition

Diamond-like carbon DLC thin films have shown advantageous field emission properties due to a negative electron . affinity NEA and low work function. The experiment was performed at substrate temperature in the range of room 2 . temperature to 6008C. The laser energy density used was in the range 6-20 Jrcm . SEM, Raman, photoluminescence PL , XPS and I-V measurement were used to investigate the microstructure and the field emission properties of DLC thin films. Deposition parameters, such as laser energy density and substrate temperature were optimized for the application of field emission properties. Good field emission properties were obtained with E s 5.03 Vrm ma t 3008C and 12 Jrcm 2 . q 2000 th

Determination of local bonding configuration and structural modification in amorphous carbon with silicon incorporation

Abstract The bonding configuration and structural evolution of Si-incorporated amorphous carbon (a-C:Si x ) films were studied. The incorporation of Si to amorphous carbon (a-C) has the advantageous effect of promoting sp 3 hybridized bond formation and improving the thermal stability. The composition, bonding configuration, structure and electrical properties of a-C:Si x were investigated as a function of Si concentration. For Si concentration below 10 at.%, incorporated Si substituted for sp 2 C-bonded clusters and the electrical resistivity of a-C:Si x increased significantly. From 10 to 23 at.%, the fraction of sp 3 bonds and the residual stress increased with Si concentration. However, when increasing Si concentration above 23 at.%, it is observed that the contribution of Si-4C bonds increased and residual stress and resistivity of a-C:Si x decreased. From the above results, different structural and bonding characteristics of a-C:Si x were established and this transition of structural evolution is closely related to the incorporated Si content in film.

Studies on the structure and bonding state of nitric amorphous carbon (a-CNx) films by reactive rf magnetron sputtering

This manuscript reports on the structure, bonding states of nitric amorphous carbon (a-CN x ) films and its correlation with electrical, optical properties with post-annealing treatment, a-CN x films were deposited on Si(100) by reactive rf magnetron sputtering using a gas mixture of Ar and N 2 . X-ray photoelectron spectroscopy revealed that there are two different C-N bonding states where N is bonded to both sp 2 and sp 3 C atoms. The amount of N-sp 3 C bond is proportional to the N/C atomic ratio in a-CN x . As the amount of N-sp 3 C bond decreased with annealing, total sp 3 /sp 2 bond ratio, resistivity, density and refractive index also decreased. Compared to amorphous carbon (a-C), a slow decrease tendency of total sp 3 /sp 2 bond ratio was observed in a-CN x due to thermal resistance of the N-sp 3 C bond.

The investigation of thermal effect on the properties of pulsed laser deposited diamond-like carbon films

Abstract The properties of diamond-like carbon (DLC) film were revealed to mainly depend on the ratio of sp 3 /sp 2 carbon bonds. In order to investigate the factors that influence the change of sp 3 /sp 2 ratio, the deposition on a substrate under heating and post-annealing treatments of DLC films has been carried out. Comparing the results from substrate heating with post-annealing treatments, it was confirmed that there is a thermal effect caused by excess thermal energy. DLC films were deposited using a pulsed laser deposition (PLD) technique on Si(100) substrates and the temperature range of substrate heating and post-annealing was varied between 25 and 500°C. The properties of DLC films according to the temperatures were analyzed by various techniques. X-ray diffractometer and Raman spectroscopy were used to evaluate the structure of DLC films and investigate the microstructural change with temperature. Rutherford backscattering spectrometry and scanning electron microscopy were used to obtain the information about the density of DLC films. The results of photoluminescence and four-point probe agreed well with the above analyses.

Micro-structural analysis of carbon nitride (CNx) film prepared by ion beam assisted magnetron sputtering

Abstract The growth and structural evolution of carbon nitride (CN x ) films, deposited by nitrogen ion beam assisted magnetron sputtering, were studied. The deposition rate, composition ([N]/[C] ratio), structure, and mechanical properties of CN x films were investigated as a function of nitrogen ion energy in the range of 30 eV–1 keV. For the ion energy below 200 eV, the increasing fraction of curved structure as revealed by transmission electron microscopy and sp 3 hybridized bonding were attributed to structural transition and improved mechanical properties of CN x films. However, when increasing nitrogen ion energy above 200 eV, the [N]/[C] ratio in film was inversely proportional to the nitrogen ion energy and preferential distribution of nitrogen in sp 2 hybridized site induced the retransition from curved structure to planar structure. From these results, it was found that CN x films exhibit two different structural and bonding characteristics with ion energy and this transition of film characteristic is closely related to the nitrogen content in the film.

Determination of bonding structure of Si, Ge, and N incorporated amorphous carbon films by near-edge x-ray absorption fine structure and ultraviolet Raman spectroscopy

This work represents a comparative analysis of bonding structure in Si, Ge, and N incorporated amorphous carbon (a-C) films using near-edge x-ray absorption fine structure (NEXAFS) and ultraviolet (UV) Raman spectroscopy. From NEXAFS analyses, changes in the π and σ bonding states of the films with Si, Ge, and N incorporation could be determined. It is also revealed that incorporation of Si, Ge, and N play a role of increasing sp3 fractions of sputtered a-C in different ways of formation of sp3 bonds. Incorporated Si and Ge atoms substitute C atoms and open up the ring structure, promoting the sp3 hybridized bonds with its neighboring atoms. Compared to Si, incorporated Ge easily facilitated the formation of sp3 hybridized bond with neighboring C atoms due to small hybridization energy. By comparing with UV Raman spectra, incorporation of N induces N substituted five-membered ring structure without destroying the ring structure. For N incorporated a-C, the increased sp3 fraction is shown to be due to five...

Investigation on the interface formation of ambient-pressure-dried SiO2 aerogel film deposited on GaAs

The interfacial state between ambient-pressure-dried aerogel and GaAs has been examined with specific emphasis on the solvent of modification. Trimethylchlorosilane (TMCS), being widely used to modify aerogel, was shown to be inadaptable due to its constitutional chlorine, which formed HCl and then etched GaAs oxides on GaAs surface. The interface of GaAs with aerogel was roughly etched from the reflection of surface microstructure of aerogel. Therefore, surface modification of aerogel with TMCS induced a great damage to interfacial GaAs surface, resulted in the change of surface characteristics of GaAs, and finally induced cracks and a collapse of aerogel fractal structure. On the contrary, hexamethyldisilazane, another modifying agent for aerogel surface, represented a relatively good interfacial state, while aerogel could be successfully formed on GaAs substrate.