scholarly journals Direct visualization of subcritical nuclei in molecular film growth

2014 ◽  
Vol 70 (a1) ◽  
pp. C1606-C1606
Author(s):  
Daniel Schwarz
Keyword(s):  
Gas Phase ◽  
Crystalline Phase ◽  
Film Growth ◽  
Careful Analysis ◽  
Acid Group ◽  
Linear Molecule ◽  
Supramolecular Network ◽  
Bright Field Image ◽  
Phenyl Rings ◽  
Different Temperatures

The growth and structure of 4,4'-biphenyldicarboxylic-acid (BDA) on Cu(001) at temperatures between 300 K and 400 K was studied by LEEM and μ-LEED. BDA is a linear molecule consisting of two phenyl rings with a carboxylic-acid group at opposite ends. During growth on Cu(001) the adsorbed BDA molecules form first a disordered 2D gas phase. Once this phase reaches a sufficiently large density, a crystalline phase nucleates, in which the molecules form a hydrogen-bonded 2D supramolecular network. By a careful analysis of the LEEM bright-field image intensity we can measure the density of the 2D gas phase, which is up to 40% of that in the crystalline phase. From the equilibrium densities at different temperatures we can construct the 2D phase diagram and extract the cohesive energy (0.35 eV). During the distinct nucleation period we can observe a fascinating phenomenon: sub-critical nuclei form, grow up to 4000 nm2in size and decay with lifetimes of several seconds. These sizes are considerably larger than what is usually seen in epitaxial growth and we explain this observation with the relatively weak intermolecular interactions.

Growth kinetics of chemically vapor deposited SiO2 films from silane oxidation

1998 ◽  
Vol 13 (8) ◽  
pp. 2308-2314 ◽  
Author(s):  
Fernando Ojeda ◽  
Alejandro Castro-García ◽  
Cristina Gómez-Aleixandre ◽  
José María Albella
Keyword(s):  
Gas Phase ◽  
Deposition Rate ◽  
Growth Kinetics ◽  
Film Growth ◽  
Chemical Vapor ◽  
Intermediate Species ◽  
Pressure Oxygen ◽  
Pressure Chemical ◽  
Different Temperatures ◽  
Kinetics Of

The growth kinetics of SiO2 thin films obtained by low-pressure chemical vapor deposition (CVD) from SiH4/O2/N2 gas mixtures has been determined at different temperatures and flow rates. The results show that the film growth is originated by some intermediate species (e.g., SiOxHy) produced in the gas phase. At low temperatures the deposition rate is limited by some homogeneous reaction with an apparent activation energy of 1.42 eV. Furthermore, the observation of critical limits when total pressure, oxygen/silane flow ratio, and temperature are decreased gives support to a branching-chain mechanism of deposition. Finally, we have observed that the deposition rate shows a hysteresis behavior when varying the temperature within the 300–400 °C range, which has been attributed to the inhibition of silane oxidation by the Si–OH surface groups of the films grown on the reactor walls.

Excimer Laser Interactions with Ptfe Relevant to thin Film Growth

1993 ◽  
Vol 334 ◽  
Author(s):  
J.T. Dickinson ◽  
M.G. Norton ◽  
J.-J. Shin ◽  
W. Jiang ◽  
S.C. Langford
Keyword(s):  
Thin Film ◽  
Gas Phase ◽  
Film Growth ◽  
Careful Analysis ◽  
Thin Film Growth ◽  
Growth Mechanisms ◽  
Definitive Evidence ◽  
Reaction Models ◽  
Thermally Driven ◽  
Insight Into

AbstractRecently, thin films of polytetrafluroethylene (PTFE) have been grown using pulsed laser ablation of TeflonTM at 266 nm.1,2 To provide further insight into the growth mechanisms we have examined the neutral and charged particle emissions generated in vacuum by 0 - 3 J/cm2 pulses of 248 nm radiation incident on solid PTFE. Measurements include quadrupole and time-of-flight mass spectroscopy. We find in addition to the neutral monomer (C2F4), copious emissions of highly reactive neutral and charged radicals, e.g., CF2, CF3, CF, F, and Cx. A careful analysis of the fluence dependence of these products provides definitive evidence that their precursors are generated by a thermally driven unzipping reaction. Models for the production of the radical species with the observed energies (several eV) involving gas phase processes are presented. Implications for improving PTFE thin film growth will be discussed.

Growth study of epitaxial FexZn1−xF2 thin films

2001 ◽  
Vol 16 (6) ◽  
pp. 1769-1775 ◽  
Author(s):  
J. McChesney ◽  
M. Hetzer ◽  
H. Shi ◽  
T. Charlton ◽  
D. Lederman
Keyword(s):  
Thin Films ◽  
Film Growth ◽  
Magnetic Phase Diagram ◽  
Epitaxial Thin Films ◽  
X Ray Diffraction ◽  
Growth Study ◽  
Lattice Match ◽  
Different Temperatures ◽  
Bulk Single Crystals ◽  
The Ideal

The FexZn1−xF2 alloy has been shown to be a model system for studying the magnetic phase diagram of dilute magnets. Whereas the growth of bulk single crystals with fixed Zn concentrations is difficult, the thin film growth is comparatively simpler and more flexible. To gain an understanding of the growth of FexZn1−xF2 films, a method was developed to grow smooth films at fixed concentrations. This was done by depositing a MgF2 buffer layer on MgF2(001) substrates and then depositing FeF2 and ZnF2 [001]-orientated epitaxial thin films at different temperatures. Surprisingly, the lattice spacing depends strongly on the growth temperature, for 44-nm-thick FeF2 films and 77-nm-thick ZnF2 films. This indicates a significant amount of stress, despite the close lattice match between the films and the MgF2 substrate. Thick alloy samples (approximately 500 nm thick) were grown by co-evaporation from the FeF2 and ZnF2 sources at the ideal temperature determined from the growth study, and their concentration was accurately determined using x-ray diffraction.

Direct Nucleation of Crystalline SiGe on Substrates by Reactive Thermal CVD with Si2H6 and GeF4

1997 ◽  
Vol 467 ◽  
Author(s):  
Fumio Yoshizawa ◽  
Kunihiro Shiota ◽  
Daisuke Inoue ◽  
Jun-ichi Hanna
Keyword(s):  
Growth Rate ◽  
Gas Phase ◽  
Heterogeneous Nucleation ◽  
Homogeneous Nucleation ◽  
Film Growth ◽  
Early Stage ◽  
Gaseous Mixture ◽  
The Other ◽  
Thermal Cvd ◽  
Initial Deposition

ABSTRACTPolycrystalline SiGe (poly-SiGe) film growth by reactive thermal CVD with a gaseous mixture of Si2H6 and GeF4 was investigated on various substrates such as Al,Cr, Pt, Si, ITO, ZnO and thermally grown SiO2.In Ge-rich film growth, SEM observation in the early stage of the film growth revealed that direct nucleation of crystallites took place on the substrates. The nucleation was governed by two different mechanisms: one was a heterogeneous nucleation on the surface and the other was a homogeneous nucleation in the gas phase. In the former case, the selective nucleation was observed at temperatures lower than 400°C on metal substrates and Si, where the activation of adsorbed GeF4 on the surface played a major role for the nuclei formation, leading to the selective film growth.On the other hand, the direct nucleation did not always take place in Si-rich film growth irrespective of the substrates and depended on the growth rate. In a growth rate of 3.6nm/min, the high crystallinity of poly-Si0.95Ge0.05in a 220nm-thick film was achieved at 450°C due to the no initial deposition of amorphous tissue on SiO2 substrates.

scholarly journals The growth of silver iodide films

1929 ◽  
Vol 125 (797) ◽  
pp. 370-394 ◽  
Keyword(s):  
Parabolic Equation ◽  
Gas Phase ◽  
Low Temperatures ◽  
Silver Iodide ◽  
Film Growth ◽  
Oxide Films ◽  
Gravimetric Method ◽  
Instructive Case ◽  
At Will ◽  
Iodide Film

It is now well established that a large class of important chemical reactions is controlled by the growth of obstructive films, but our knowledge of the mechanism of the growth of such films—especially at low temperatures—is still very imperfect. The present paper describes a detailed study of a particularly instructive case of film-growth, the action of iodine on silver; this reaction was chosen because silver iodide films—in contrast with oxide films—reach visible thickness rapidly at ordinary temperatures. The optical properties of these films have already been studied by Wernick, whilst much information regarding the velocity of film-growth has been obtained by Tammanm by Kohlschutter and Krahenbiihl, and by Hartung. Tammann used the interference colour as the means of arriving at the thickness of the film; this method has certain unique advantages, but the more recent work of Tammann and Bockow has indicated that—in the case of oxide-films at least—the particular form of the method employed gives values for the thickness differing widely from those obtained by the gravimetric method. Tammann expressed the relation between the thickness ( y ) and the time ( t ) by the parabolic equation y 2 = 2 pt , where p is a. constant. Kohlschütter and Krähenbiihl, and also Hartung, used microgravimetric methods to determine the amount of iodine taken up, and obtained curves connecting thickness and time ; these curves do not appear to follow the parabolic equation. All the experimenters mentioned used iodine vapour to attack the silver, but the concentration of iodine in the gas phase was not directly determined. In all cases the surfaces were prepared in air, and the possible effect of exposure to oxygen was not considered; yet in several of the reactions of copper and iron, pre-exposure to air or oxygen is known greatly to modify the result, owing to the fact that an oxide-film may become protective before reaching the thickness needed for interference colours. It may be mentioned that after exposure to vapour, the colour produced on metallic specimens is usually not uniform, but indicates a greater film-thickness near the edge. In the present research, it was decided to use a solution of iodine in an organic solvent; in this case, the concentration could be fixed or varied at will, and in general uniform colouration (indicating uniform thickness) could be obtained. Moreover, abrasion could be conducted, if required, below the surface of the solvent, instead of in air. Chloroform was .found to be a suitable liquid, since, whilst freely dissolving iodine, it had no appreciable solvent action on a silver iodide film.

Mechanism of Chromium Deposition from Cr(CO)6 by Uv Laser Light

1989 ◽  
Vol 158 ◽  
Author(s):  
R. Nowak ◽  
P. Hess
Keyword(s):  
Gas Phase ◽  
Metal Film ◽  
Film Growth ◽  
Laser Light ◽  
Film Deposition ◽  
Uv Laser ◽  
Impurity Incorporation ◽  
Metal Atoms ◽  
Chromium Films ◽  
Main Growth

ABSTRACTThe mechanism of metal film deposition from carbonyls as precursors is discussed in detail. It is shown that different species produced by UV laser irradiation in the gas phase contribute to film growth. Highly reactive species such as metal atoms may be important during the nucleation phase, whereas more stable carbonyls are responsible for the main growth process. This indicates that the main decarbonylation effect occurs at the surface. The higher level of impurity incorporation in chromium films in comparison with nickel films is explained by the relative position of the Fermi level in the d-band of Ni and Cr with respect to the 2π* level of CO, which favors CO bond dissociation in the case of chromium.

A Study on CVD TaN as a Diffusion Barrier for Cu Interconnects

2000 ◽  
Vol 612 ◽  
Author(s):  
Se-Joon Im ◽  
Soo-Hyun Kim ◽  
Ki-Chul Park ◽  
Sung-Lae Cho ◽  
Ki-Bum Kim
Keyword(s):  
Activation Energy ◽  
Gas Phase ◽  
Diffusion Barrier ◽  
Surface Reaction ◽  
Film Growth ◽  
Ion Beam ◽  
Barrier Properties ◽  
Tantalum Nitride ◽  
X Ray Diffraction ◽  
X Ray

AbstractTantalum nitride (TaN) films were deposited using pentakis-diethylamido-tantalum [PDEAT, Ta(N(C2H5)2)5] as a precursor. During film growth, N- and Ar-ion beams with an energy of 120 eV were supplied in order to improve the film quality. In case of thermallydecomposed films, the deposition rate is controlled by the surface reaction up to about 350 °C with an activation energy of about 1.07 eV. The activation energy of the surface reaction controlled regime is decreased to 0.26 eV when the Ar-beam is applied. However, in case of Nbeam bombarded films, the deposition is controlled by the precursor diffusion in gas phase at the whole temperature range. By using Ar-beam, the resistivity of the film is drastically reduced from approximately 10000 µω-cm to 600 µω-cm and the density of the film is increased from 5.85 g/cm3 to 8.26 g/cm3, as compared with thermally-decomposed film. The use of N-beam also considerably lowers the resistivity of films (∼ 800 µω-cm) and increases the density of the films (7.5 g/cm3). Finally, the diffusion barrier properties of 50-nm-thick TaN films for Cu were investigated aftre annealing by X-ray diffraction analysis. The films deposited using N- and Arbeam showed the Cu3Si formation after annealing at 650 °C for 1 hour, while thermallydecomposed films showed Cu3Si peaks firstly after annealing at 600 °C. It is considered that the improvements of the diffusion barrier performance of the films deposited using N- and Ar-ion beam are the consequence of the film densification resulting from the ion bombardment during film growth.

Research on the Temperature Field and Roast Mechanism of Blast Furnace Tap-Hole Clay

2011 ◽  
Vol 189-193 ◽  
pp. 1370-1375
Author(s):  
Shi Ling Yang ◽  
Jian Hua Zhang ◽  
Ying Dong ◽  
Xue Jie Cao
Keyword(s):  
Temperature Field ◽  
Blast Furnace ◽  
High Temperature ◽  
Crystalline Phase ◽  
Air Permeability ◽  
High Temperature Strength ◽  
Coke Structure ◽  
Mullite Phase ◽  
Different Temperatures ◽  
Abaqus Software

The temperature field of blast furnace tap hole clay was analyzed by using ABAQUS software. Samples taken from the tap-hole clay in depth of 1200mm, 2200mm, 2600mm and 2800mm after roasted for 100 minutes were studied by using XRD and SEM to investigate their roast mechanism and microstructure at different temperatures. The results show that the ore phase of the tap-hole clay in depth of 1200mm remained unchanged but only tar and asphalt appear the carbonation phenomena. There is a large number of SiC crystalline phase appears in depth of 2200mm. At the same time, porosity increases and coke structure is formed. The air permeability is enhanced. In the tap-hole clay of 2600mm～2800mm depth, elongated rod-likeβ-Si3N4 grains obviously increase while the SiC grains decrease. A large number of high-temperature flocculent mullite phase appears and the high-temperature strength of the tap-hole clay is strengthened.

Predictive Surface Kinetic Analysis: The Case of TiSi2 CVD

1993 ◽  
Vol 334 ◽  
Author(s):  
M. A. Mendicino ◽  
R. P. Southwell ◽  
E. G. Seebauer
Keyword(s):  
Gas Phase ◽  
Film Growth ◽  
Growth Conditions ◽  
Si Substrate ◽  
Quantitative Correlation ◽  
Selective Area ◽  
Metal Silicides ◽  
High Production ◽  
Reaction Stoichiometry ◽  
Area Deposition

Recently, TiSi2 has been the object of considerable study because of its low resistivity among the transition metal silicides and its compatibility with existing ULSI technology [1,2]. Film growth by CVD offers the potential for selective area deposition and high production throughput. However, selective CVD of TiSi2 from gas phase SiH4 and TiCl4 is usually accompanied by a competing reaction which consumes intolerable amounts of the Si substrate [3,4]. Controlling this consumption is crucial in TiSi2 growth; however, no quantitative correlation exists between silicon consumption and growth conditions or film thickness. Additionally, the reaction mechanism for TiSi2 growth is poorly understood, and some disagreement even exists about the reaction stoichiometry [5,6]. The combined CVD/UHV approach we have developed fills many gaps in the current understanding of TiSi2 CVD.

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