摘要:

Gas‐source molecular beam epitaxy (GS‐MBE), utilizing Ga and NH3, and reactive‐ion MBE (RIMBE), incorporating both thermal NH3and low‐energy NH+xions, were used to grow single crystal GaN(0001) layers on Al2O3(0001) at temperaturesTsbetween 700 and 850 °C with deposition rates of 0.2–0.5 μm h−1. The RIMBE experiments were carried out with incident NH+x/Ga flux ratiosJNH+x/JGa=1.9–3.2 and NH+xacceleration energiesENH+x=45–90 eV. Plan‐view and cross‐sectional transmission electron microscopy analyses showed that the primary defects in the GS‐MBE films were threading dislocations having either pure edge or mixed edge/screw characteristics with Burgers vectorsb̄=1/3〈21̄1̄0〉, basal‐plane stacking faults with displacement vectorsR̄=1/6〈022̄3〉, and prismatic stacking faults withR̄=1/2〈1̄101〉. In the case of RIMBE films, no stacking faults or residual ion‐induced defects were observed withENH+x=45 eV andTs≥800 °C. However, increasingENH+xto ≥60 eV atTs=800 °C gave rise to the formation of residual ion‐induced point‐defect clusters observable by transmission electron microscopy (TEM). IncreasingTsto 850 °C withENH+x≥60 eV resulted in the ion‐induced defects aggregating to form interstitial basal and prismatic dislocation loops, whose number densities depended upon the ion flux, with Burgers vectors 1/2〈0001〉 and 1/3〈21̄1̄0〉, respectively. Unlike previously published results for RIMBE growth with N+2, GaN growth kinetics with NH+xwere not found to be a strong function of either ion‐to‐thermal flux ratios or ion acceleration energies.

ISSN:0734-2101    

DOI:10.1116/1.579512

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Ti(Y)N and TiN coatings were deposited by the reactive ion plating method. Phase identification and examination of the texture of Ti(Y)N and TiN coatings were performed using x‐ray diffraction analysis. The addition of yttrium causes a strong modification of the growth orientation of TiN crystallites in the coating. The distribution of yttrium across the interface of the Ti(Y)N coating and the substrate was analyzed by means of electron probe microanalysis. The rare‐earth element Y was concentrated in the transition zone between the TiN coating and the substrate. The interfacial structure of the Ti(Y)N coating to the substrate was studied by transmission electron microscopy. The influence of the interface structure on the adhesion of the coating to the substrate is also discussed. The corrosion resistance and the wear resistance of the Ti(Y)N coatings were also studied. The results show that the Ti(Y)N coating exhibits an excellent corrosion resistance and high wear resistance that are improved compared to TiN by the presence of yttrium.

ISSN:0734-2101    

DOI:10.1116/1.579513

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

A comprehensive interpretation of the preferred orientations (PO) of poly‐Si films prepared from various vapor‐phase methods is presented. Existing theories and models are examined by comparing a wide variety of experimental results of PO published so far. Preferential nucleation and the conventional concept of the surface free energy are found to apply only to a limited range of deposition parameters. On the other hand, a combination of two concepts, i.e., the microscopic geometry of growing surfaces and the surface kinetics, proves to be very important in interpreting the wide variation of PO. The concept of the microscopic geometry of the surface considers the minimum numbers of atoms and bonds required for nucleation, lateral growth, and etching that characterizes the growth ability of planes. In addition, interpretation of the deposition parameter dependencies of the PO requires the concept of surface kinetics including diffusion of precursors, hydrogen coverage, and the surface reaction time which depends on the substrate temperature and gas pressure. The combined concepts can account for most of the observed POs (mainly 〈100〉 and 〈110〉) which depend on feed gases and the deposition parameters. Other specific growth modes such as facet growth or microtwins are considered for the 〈111〉 PO. The POs forn‐ andp‐type doped films are different from those of undoped films, and their origin is also discussed in terms of their growth rates.

ISSN:0734-2101    

DOI:10.1116/1.579514

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Thin films were deposited from low molecular weight polytetrafluoroethylene source materials by an ionization‐assisted evaporation method, and their crystallinity and molecular orientation were studied by x‐ray diffraction and infrared spectroscopy. The film properties were largely influenced by the substrate temperature and the molecular weight of the source material. At lower substrate temperatures, the molecules were oriented with the chain axis parallel to the substrate surface, and the film had preferential crystal orientation with the (100) plane of the hexagonal structure parallel to the substrate. With increasing substrate temperature, the molecules lost parallel orientation and the film crystallinity decreased. Such changes took place upon increasing the substrate temperature from 180 to 240 °C when deposited from a source material with a molecular weight of 8500, and from room temperature to 130 °C when the source molecular weight was 1500.

ISSN:0734-2101    

DOI:10.1116/1.579515

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

We describe an independently valved solid arsenic and phosphorus effusion source for molecular beam epitaxy. A common posteffusion hot zone and orifice ensure constant flux ratios of arsenic, phosphorus, and mixed species in the beam. With this source, we have demonstrated molecular beam epitaxial growth of GaAs1−xPxlayers with better than ±0.4% compositional variation over a 3‐in.‐diam substrate.

ISSN:0734-2101    

DOI:10.1116/1.579516

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Comparative studies were performed on the chemical composition, crystal structure, adhesion, and color of titanium–nitrogen films prepared by an electron beam thermal evaporation process. Several parameters, deposition rate, nitrogen flow rate, substrate temperature, and nitrogen inlet location, were varied during sample preparation. The composition of the films was determined by electron probe microanalysis, the crystal structure by grazing angle x‐ray diffraction, and the adhesion characteristics by scratch test analysis. Glass substrates were used to allow for visual inspection of the substrate–film interface layer. Titanium–nitrogen films with nitrogen contents varying between 7.61 and 32.5 wt % were produced. Over this range, three structures were deposited: α‐TiN0.3for low nitrogen contents, Ti2N for films of 12.2–13.1 wt % nitrogen, and TiN for films with higher nitrogen contents. The films exhibited a wide range of colors that could be related to other properties such as nitrogen content and adhesion.

ISSN:0734-2101    

DOI:10.1116/1.579517

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Epitaxial layers of the ternary alloy SiGeC were grown on 〈100〉 Si substrates. Using a rapid thermal chemical vapor deposition reactor working at low temperature and reduced pressure (550 °C and 1 Torr), we obtained SiGeC layers with a carbon concentration into substitutional sites of up to 1.5%. We used two methods to measure the substitutional C fraction in the SiGeC samples: Fourier transform infrared measurements at room temperature and x‐ray diffraction of thed004atomic distance in the alloys. Using methylsilane (SiH3CH3or MS) as the carbon precursor, we measured an activation energy for Si0.845Ge0.15C0.005growth of around 52 kcal/mol and showed that C incorporation into substitutional sites saturates at high MS flows. Finally, thermal annealing of these ternary alloys has been studied: a 800 °C annealing for 15 min leads to oxygen and carbon diffusion, whereas strain relaxation occurs by amorphous SiC precipitation with a 900 °C, 15 min annealing.

ISSN:0734-2101    

DOI:10.1116/1.579518

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Using transmission electron microscopy (TEM), we have analyzed stacking fault pyramids found in multiple implant silicon‐on‐insulator material. From a comparison of computer simulations with weak‐beam TEM images, and from the constraints imposed by crystallography, we have found that the Burgers vectors of the pyramidal stair‐rod dislocations are edge dislocations with the Burgers vector 1/3〈100〉. We have also determined that the stacking faults in these pyramids are intrinsic, and therefore probably formed through vacancy condensation.

ISSN:0734-2101    

DOI:10.1116/1.579519

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Polyphenylene oxide (PPO) films have been electrochemically deposited onto gold substrates, yielding ultrathin films on the order of 10 nm. The deposition was monitored byinsituellipsometry in real time, in order to follow the growth and determine the mechanism. The films were subsequently characterized byexsituspectroscopic ellipsometry to confirm the final film thickness and growth rate. A combination of ellipsometry and atomic force microscopy observations made in the early and final stages of film formation suggest that a nucleation regime exists. Initially, deposition occurs quickly and is then followed by mass transport controlled growth. A diffusion coefficient of 1.0×10−15cm2/s was calculated for phenol through a 5 nm PPO film. Two rate constants were determined, one for initial deposition (k1=4.7×10−1s−1) and another for the diffusion controlled regime (k2=6.8×10−5s−1).

ISSN:0734-2101    

DOI:10.1116/1.579520

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Insituattenuated total reflection Fourier transform infrared (ATR‐FTIR) spectroscopy was used to study surface processes during plasma enhanced chemical vapor deposition (PECVD) of silicon dioxide through tetraethoxysilane (TEOS) and oxygen. ATR‐FTIR studies were conducted on thin (about 50 Å) silicon dioxide films deposited on GaAs. This approach allowed us to obtain the infrared spectrum of TEOS adsorbed on SiO2in the spectral region 4000–770 cm−1and to determine the surface species and their relative surface concentrations as a function of deposition conditions in a helical resonator plasma reactor. Studies were conducted where the SiO2surface was exposed to TEOS and O2plasma sequentially and/or simultaneously. Surface processes were studied as a function of exposure to TEOS and substrate temperature.InsituATR‐FTIR studies of adsorption of TEOS on the SiO2surface show that TEOS adsorbs chemically and irreversibly onto the SiO2surface above 100 °C. SiO2growth was found to occur even without an oxygen plasma at temperatures as low as 200 °C, albeit very slowly. Below 100 °C TEOS was also found to adsorb physically: The extent of the physically adsorbed state was found to increase with decreasing temperature. Hence, during PECVD of SiO2below 100 °C, physically adsorbed TEOS can be trapped in the growing oxide giving rise to increased ethoxy and OH species which in turn adversely affect the film integrity and quality.The ATR‐FTIR studies of the surface exposed to TEOS at various temperatures indicate that the chemical adsorption of TEOS onto SiO2proceeds through a precursor‐mediated adsorption mechanism where the precursor is a physically adsorbed TEOS molecule. Exposure of adsorbed TEOS to O atoms (oxygen plasma) removed the ethoxy ligands of the surface ethoxysiloxanes, produced surface SiOH species as reaction product, and resulted in deposition of SiO2.Insituand real time studies of the actual PECVD process revealed that water and SiOH species are formed as intermediate surface reaction products and subsequent reaction and elimination of the silanol species can become the rate limiting step (as far as SiOH incorporation in the film is concerned) if the deposition rate is too high.

ISSN:0734-2101    

DOI:10.1116/1.579521

出版商:American Vacuum Society    

年代:1995

数据来源: AIP