摘要:

One‐dimensional harmonic oscillator theory was used to model tapping‐mode atomic force microscope (TMAFM) operation in the near‐contact region in the presence of gases and liquids. The force derivative of the tip‐sample interaction changes the vibration amplitude and frequency at maximum amplitude of the cantilever. Additionally, the interaction is hydrodynamically damped by fluid motion around the tip and between the tip and the surface. Good agreement was found between theoretical and experimental amplitude as a function of height. For a sample‐driven TMAFM operating in fluids, the cantilever can be very soft (spring constant ≪1 N/m) and operated at frequencies well above the fundamental. Under these conditions the cantilever and sample appear to act with a high spring constant, much like that used in a gaseous operation. The tip–sample interaction in the fluid is still mediated through the force derivative of the sample. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360304

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have investigated the annealing temperature dependence of structural and electrical properties in heavily arsenic implanted GaAs which has a similar amount of excess arsenic to low temperature GaAs (LT‐GaAs). The fundamental properties of this material are quite similar to those of LT‐GaAs. High resolution x‐ray diffraction measurements have revealed that it has an increased lattice constant, which is reduced to the value of bulk GaAs by annealing between 300 and 400 °C. Electrical conduction in this material is dominated by hopping between deep states, which is also reduced by annealing above 350 °C. In samples annealed at temperatures ranging from 600 to 850 °C, the dominant electron trap isEL2; it has been confirmed by resistivity measurements withn‐i‐nstructures that the Fermi level is pinned byEL2. In samples annealed below 500 °C, the dominant electron trap is notEL2 but theU‐band, although electron paramagnetic resonance measurements show the existence of a large concentration of the ionized arsenic antisite defect (AsGa+). This supports the notion that theU‐band is formed by AsGadefects with slightly modified carrier emission properties compared withEL2. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360235

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

1‐MeV electron irradiation effects on molecular beam epitaxy‐grown AlGaAs and InGaAs solar cells have been determined and compared with our previous results for radiation damage of InP and GaAs solar cells in order to clarify radiation resistance of compound semiconductor solar cells. Differences of radiation resistance of AlGaAs, GaAs, and InGaAs cells are found to be explained by band‐gap energy effects on solar cell degradation. Moreover, 1‐MeV electron irradiation results of several solar cells such as InP, InGaP, InGaAsP, GaAs, AlGaAs, InGaAs, Si, Ge, and CuInSe2have also been analyzed by considering their damage constants, band‐gap energies, and optical absorption coefficients. It is found that superior radiation‐resistance of CuInSe2and InP‐based solar cells is explained by the higher optical absorption coefficient of CuInSe2and lower defect introduction rates (damage constants) of InP‐based materials compared to other compound semiconductor materials. ©1995 American Institute of Physics. 

ISSN:0021-8979    

DOI:10.1063/1.360236

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Deep levels and carrier compensation created in undoped metal‐organic chemical‐vapor deposition grown GaAs by low fluence proton irradiation (1×108−1×1010cm−2) are investigated by the deep level transient spectroscopy technique and capacitance‐voltage profiling. At least five main electron traps are observed after room‐temperature irradiation in addition to theEL2 present in the as‐grown material. Irradiation generates additionalEL2, which annihilate at much lower temperatures than one would expect for isolatedEL2. However, with further increase in irradiation fluence, the magnitude for this additional increment begin to decrease. The apparent decrease in theEL2 peak is accompanied by an increase of a broad peak in the deep level transient spectroscopic spectrum. This broad peak has a highly nonexponential capacitance transient and it is suggested to result from the interaction of the additionalEL2 withEL6. One of the observed traps, with energy level, (Ec−0.40) eV, has not previously been reported in proton irradiated GaAs. The signature of this trap resembles that ofEL5 and is quite stable at moderate annealing temperatures; annihilating completely only at a temperature of ∼600 °C. This level shows a saturation effect with increasing irradiation dose and we believe it is related to complex defect‐impurity formation. The temperature dependence of the carrier profiles reveals some complex behavior of carrier compensation, including acceptor‐ and donor‐like properties of the various traps. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360237

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Etching of a chemical‐beam‐epitaxy‐grown InP/InGaAs multilayer structure with reactive ion etching (RIE) and laser‐assisted dry etching ablation (LADEA) is carried out in order to evaluate the extent of the damage induced by these two etching methods. Micro‐Raman spectroscopy indicates a systematic broadening of the phonon lines as a function of depth of a RIE fabricated crater. In contrast, LADEA which is based on the application of an excimer laser for the removal of the products of chemical reaction, shows no measurable changes in the phonon line widths when compared to as‐grown material. The results suggest that LADEA has potential for the photoresistless fabrication of damage free microstructures. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360763

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The dependence of the effective segregation coefficient (ke) on the growth rate (R) has been investigated by the necking method using phosphorous as an impurity in the silicon melt growth process. The investigations were carried out for two different growth orientations of the silicon crystal, ⟨100⟩ and ⟨111⟩. The coefficient increased with increasing growth rate for both crystal orientations. The behavior in the relatively lower growth rate region is explained by the BPS model. However, the coefficient in the higher growth rate region is larger than that expected by the BPS theory. Additionally, the critical growth rate (R*), where the value of the coefficient deviates from the theory, depends on the growing crystal orientation. TheR* in the ⟨111⟩ crystal is lower (∼0.5 mm/min) than that in the ⟨100⟩ crystal (∼3.0 mm/min). ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360238

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The substitutional gold concentration introduced in silicon by a diffusion step between 850 and 1000 °C was measured by deep level transient spectroscopy both in floating zone (FZ) and Czochralski (Cz) silicon containing different dislocation densities. The comparison, in the same sample, of dislocated and undislocated regions allows the efficiency of dislocations as sinks for self‐interstitials &ggr; to be measured as a function of diffusion temperature. In FZ silicon &ggr; was found independent of temperature whereas in Cz silicon a remarkable temperature dependence for &ggr; was observed which can be attributed to the release of dislocations by a thermally stimulated climbing mechanism from obstacles (i.e., oxygen segregation or precipitation). ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360239

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

To study effects of ion implantation with the energy scanning mode on the surface structure and the depth profile, Zr samples were implanted with15N2ions, where ion energy was scanned in the range of 70–100 and 70–130 keV using a computer‐controlled power supply at an interval of 2 keV while monitoring the ion current of the sample. After the implantation of a total fluence of 3.5×1017ions/cm2, the depth profiles of15N2ions in Zr were measured by nuclear reaction analysis of15N(p,&agr;&ggr;)12C at 429 keV and the surface was observed by scanning electron microscopy. It was found that the implanted surface structure strongly depended on the implantation mode, and blistering induced by high fluence implantation of nitrogen could be completely avoided with the implantation mode of increasing energy gradually. The depth profiles were satisfactorily in agreement with the prediction by Monte Carlo simulation. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360240

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A decrease in the thermal conductivity and the optical absorption length of a silicon wafer damaged by ion implantation causes an increase in the amplitude of photoacoustic displacement (PAD) on the sample surface. The behaviors of the PAD were investigated by thermoelastic analysis. The theoretical results indicate that the amplitude of PAD is approximately proportional to the square of the thickness of the damaged layer and is characterized by the ratio of the optical‐absorption coefficient to the thermal conductivity of the damaged layer. Experimental results, which were quantitatively measured by a highly sensitive PAD interferometer, can be explained well by the theoretical predictions. The thermal conductivity of the damaged layer by implantation above critical amorphization dose can be estimated to be 1–3 W/mK by comparison of the experimental data with the theoretical results. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360241

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Annihilation characteristics of positrons in various types of diamonds were studied by measurements of two‐dimensional angular correlation of positron annihilation, those of Doppler Broadening profiles and those of lifetime spectra. From the measurements, it was found that there is a small amount of defects in type Ib synthesized diamond and the positron lifetime is 115 ps. On the other hand, it was found that positronium is formed in natural diamonds. Results of the double x‐ray measurements suggested that IIa, IIb, and Ia type natural diamonds also may have empty space between crystallites or grain boundaries. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360242

出版商:AIP    

年代:1995

数据来源: AIP