摘要:

Single‐crystal Si films have been grown on Si(001)2×1 substrates by ultraviolet (UV) photostimulated atomic‐layer epitaxy (ALE) from Si2H6. The ALE deposition rate R per growth cycle remains constant at 0.4 monolayers (ML), 1 ML=6.8×1014cm−2, over a wide range of deposition parameters: growth temperature (Ts=180 –400 °C), Si2H6exposure (peak pressure during gas pulse=0.1–5 mTorr), UV laser energy density (E=250–450 mJ cm−2whereEmaxis determined byTs), and number of UV laser pulses per cycle. A film growth model, based upon the results of the present deposition experiments and Monte Carlo simulations, together with our previous adsorption/desorption measurements, is used to describe the reaction pathway for the process. Si2H6is dissociatively adsorbed on Si surface dimers as two SiH3radicals which subsequently dissociate to SiH2and H. Site blocking during the adsorption and surface dissociation steps limits the surface coverage to 2.9×1014SiH2cm−2(hence,R=0.43 ML per cycle). The H terminated silylene‐saturated surface is thermally stable and passive to further Si2H6exposure. ArF or KrF laser pulses (≊20 ns) are used to desorb H, following a Si2H6exposure, and the growth cycle is repeated until the desired film thickness is obtained. AtTs400 °C, H is thermally desorbed and pyrolytic growth competes with ALE. Plan‐view and cross‐sectional transmission electron micrographs together with selected‐area and convergent‐beam electron diffraction patterns show that the ALE films are epitaxial layers with no observed extended defects or strain.

ISSN:0734-2101    

DOI:10.1116/1.577164

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

We investigated the influence of a hydrogenated disordered carbon (a‐C:H) layer on the nucleation of diamond. Substratesc‐Si〈100〉, SiAlON, and highly oriented pyrolytic graphite {0001} were used in this study. The substrate surfaces were characterized with Auger electron spectroscopy (AES) while diamond growth was followed with Raman spectroscopy and scanning electron microscopy (SEM). It was found that on silicon and SiAlON substrates the presence of thea‐C:H layer enabled diamond to grow readily without any polishing treatment. Moreover, more continuous diamond films could be grown when the substrate was polished with diamond powder prior to the deposition of thea‐C:H layer. This important result suggests that the nucleation of diamond occurs readily on disordered carbon surfaces, and that the formation of this type of layer is indeed one step in the diamond nucleation mechanism. Altogether, the data refute the argument that silicon defects play a direct role in the nucleation process. Auger spectra revealed that for short deposition times and untreated silicon surfaces, the deposited layer corresponds to an amorphous carbon layer. In these cases, the subsequent diamond nucleation was found to be limited. However, when the diamond nucleation density was found to be high; i.e., after lengthy deposits ofa‐C:H or after diamond polishing, the Auger spectra suggested diamondlike carbon layers.

ISSN:0734-2101    

DOI:10.1116/1.577165

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

A successful attempt to grow the Pd–Te intermetallic compounds on 2H–MoS2(0001) surfaces by molecular beam epitaxy will be reported. When a Te2molecular beam alone impinges onto the 2H–MoS2(0001) substrate, the sticking coefficient is found to decrease with increasing substrate temperature (Ts) and to become zero atTs≥470 K. The sticking coefficient of the Te2molecules impinging simultaneously with a Pd beam, however, is finite even at temperatures above 470 K. Under the simultaneous impinging condition, three kinds of intermetallic compounds: PdTe2(001), PdTe(001), Pd9Te4(010) are found to grow heteroepitaxially. The phase formed in the film depends on the flux ratio and the substrate temperature. The resultant phase diagram is explained quantitatively by considering a capture rate of Te molecules by the arriving Pd atoms.

ISSN:0734-2101    

DOI:10.1116/1.577166

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

The (1̄1̄1̄) CdTe surface is studied by reflection high energy electron diffraction, x‐ray photoelectron spectroscopy, and x‐ray photoelectron diffraction (XRD). Several surface reconstructions are described. Shifts in the Cd (3d) binding energy levels allow separation of contribution of surface Cd atoms from that of the bulk. While bulk atoms exhibit XPD effects along the standard crystallographic directions, for surface atoms the diffraction effects occur along distinct directions which correspond to an outwards relaxation of the topmost Te layer. These findings are consistent with a recently proposed model of the CdTe (1̄1̄1̄) surface.

ISSN:0734-2101    

DOI:10.1116/1.577167

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

An XeCl excimer laser was used to grow thin polycrystalline films of the ternary alloy semiconductor, ZnSexTe1−x, on sodium‐free glass substrates. The laser ablation/evaporation process has produced films spanning the entire compositional range withxvalues close to those of the original target. At a typical growth temperature of 300 °C, the grains possess orientations which vary from a predominant 〈111〉 for ZnTe to 〈311〉 for ZnSe with an increasing fraction of 〈311〉 as the ZnSe fraction increases. X‐ray diffraction shows that the alloy lattice constant increases linearly with thexvalue, absorption measurements show band bowing similar to that observed in bulk single crystals, and Raman studies show that the lattice dynamics are characteristic of single‐vibrational‐mode behavior over the entire alloy range.

ISSN:0734-2101    

DOI:10.1116/1.577168

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

Titanium–oxide films were deposited on Si wafers and/or quartz plates by a dynamic ion beam mixing method. High energy O+2and/or O+beams (30–40 keV) were injected during the deposition of Ti vapor onto the samples. Analysis of the film structure revealed the formation of TiO rather than TiO2, and the film growth varied from (111) to (200) plane of TiO with a decrease in the Ti:O arrival rate of Ti atoms and O+ions onto the sample. Annealing of prepared films at 600 °C in the open air changed the film structure to include TiO2.

ISSN:0734-2101    

DOI:10.1116/1.577169

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

Tin oxide films were deposited by organometallic chemical vapor deposition using tetramethyltin and oxygen as reactants. Possibilities for single crystal growth were investigated by depositing thin films at various growth conditions and on several different orientations of rutile titania and sapphire single crystal substrates. Single crystal films were deposited on titania (110) oriented crystals. The morphology of these films appears practically featureless at 40 kx in a scanning electron microscope. Atomic resolution images of these films were also obtained using atomic force microscopy. Highly textured polycrystalline films were grown on rutile titania (100), (001), and (111) oriented single crystals. X‐ray diffraction results show that the orientation of these films follows that of the substrate. Single crystal films having a submicron sized morphology were deposited on sapphire (11̄02) crystals. Films grown on sapphire (0001) substrates are polycrystalline and show strong (200) or (110) texture depending on the growth conditions. Highly (110) textured films were also deposited on fused quartz substrates at growth temperatures below 475 °C and deposition rates lower than 0.3 μm/h. The dependence of film morphology and preferred orientation on substrate and growth conditions is discussed.

ISSN:0734-2101    

DOI:10.1116/1.577170

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

Single layer films of CeO2have been deposited both by conventional electron beam evaporation and ion assisted deposition with oxygen and argon ions. A broad beam Kaufman ion source (3 cm diam) has been used to generate the ions. A systematic study has been made on optical properties such as refractive index, extinction coefficient and inhomogeneity of the films as a function of: (1) oxygen partial pressure in the range 1×10−4to 1×10−5mbar. (2) Incidence of oxygen ions with energy in the range 300–700 eV and current density in the range 50–220 μA/cm2. (3) Incidence of mixed argon and oxygen ions of different ratios. The refractive index of the films deposited under the influence of ion bombardment showed higher indices than the conventionally evaporated films. The maximum index obtained with an oxygen ion bombardment was 2.3 at an ion energy of 600 eV and current density of 220 μA/cm2. The bombardment of the films with a mixed argon–oxygen (25% Ar) ion beam of the same energy and current density was found to further increase the refractive index. The extinction coefficient in both cases was negligible.

ISSN:0734-2101    

DOI:10.1116/1.577171

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

Yttria‐stabilized zirconia (YSZ) thin films were deposited by reactive magnetron sputter deposition from a composite Zr–Y target in Ar–O2mixtures. Hysteresis was observed as a function of oxygen flow rate f. For a discharge current of 0.4 A and a total pressurePof 5 mTorr, for example, the target oxidized at f>2.3 ml/min, with the reverse transition from an oxidized to a metallic target surface occurring at 1.95 ml/min. The deposition rate was 2.7 μm/h in the metallic mode and 0.1 μm/h in the oxide mode. Fully oxidized (Y2O3)0.1(ZrO2)0.9was obtained forf>2.0 ml/min, even in the metallic mode. While films deposited withP=3–20 mTorr were continuous, forP>20 mTorr crazing was apparent as expected for a ceramic film in a tensile stress state. ForP<3 mTorr, the films delaminated due to excessive compressive stress. X‐ray diffraction and electron microscopy results showed that the films were polycrystalline cubic YSZ with a columnar structure and an average grain diameter of 15 nm. Fully dense films were obtained at a deposition temperature of 350 °C. Temperature‐dependent impedance spectroscopy analysis of YSZ films with Ag electrodes showed that the oxygen ion conductivity was as expected for YSZ.

ISSN:0734-2101    

DOI:10.1116/1.577172

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

A new electron beam source was developed according to ultrahigh vacuum design rules. It is rate controlled by means of a quadrupole mass spectrometer based flux meter. Preprogrammed and stored wobble patterns with a large frequency range prior and (for most materials) during evaporation improve the performance of operation and enable a high utilization of the material. A very stable operation is achieved by simultaneously controlling not only the power but also the power density. Long term stability, material utilization, dynamic range, minimum controllable rate and reproducibility were investigated especially for Si molecular beam epitaxy.

ISSN:0734-2101    

DOI:10.1116/1.577173

出版商:American Vacuum Society    

年代:1991

数据来源: AIP