摘要:

Electro‐optical characteristics related to the threshold behavior of liquid crystals when using the in‐plane switching (IPS) mode were investigated with interdigital electrodes. In order to analyze the switching behavior of liquid crystals, an equation, which expresses the threshold transition, was derived using the continuum elastic theory. It was made clear that it was the electric field and not the voltage that drives the liquid crystals in the IPS mode. Significantly, an inversely proportional relationship between the threshold voltage and the gap between the substrates was found to hold. Furthermore, the electro‐optical characteristics were recognized to change with the variation of the gap between the substrates. This behavior is due to the independence of electric field on liquid crystal layer normal. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115309

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

In a hot‐filament reactor diamond films were deposited on various substrates without pretreatment. A nickel wire placed at a short distance above the substrate yields an increase of the nucleation density by five orders of magnitude. Closed diamond films were obtained for different substrate materials. The deposits were characterized by scanning electron microscopy, Raman spectroscopy, and x‐ray photoelectron spectroscopy. The presence of Ni in the diamond films indicates that Ni containing species are transported through the gas phase during the reaction to the substrate surface thus forming nucleation centers. Replacing the Ni wire by a diamond membrane nucleation enhancement is reduced by about three orders of magnitude. The pronounced distance dependence observed suggests that volatile unstable species are produced which form nucleation centers upon impact on the substrate surface. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115310

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

High‐quality C60(111) overlayers are grown on Au(111)/Ag(111)/mica substrates and their structures studied by x‐ray diffraction. The structural evolution of these overlayers is investigated for growth temperatures from 120 to 290 °C. C60(111) overlayers undergo an in‐plane orientational reordering atTo∼150 °C. Above this temperature, the rotated and commensurate in‐plane structures coexist with each other. The rotated structures evolve from the in‐plane structures, which predominate at temperatures belowTo. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115311

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A powdery sample of CaH2heated to ∼730–790 K in a readily attainable high vacuum (∼1 ×10−7Torr) was found to emit thermal electrons (∼ 10−7–10−5A) and H−ions (∼ 10−15–10−12A, mass analyzed) from its surface (∼ 0.1 cm2). The work function of the sample and the desorption energy of H−were 4.8 ± 0.1 and 7.4 ± 0.2 eV, respectively. The latter fairly agreed with the value (7.1 ± 0.1 eV) derived theoretically by our simple model for the thermal negative ion emission. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115312

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

This letter discusses the optical properties ofCr3+ions in mixed borate crystals with the formulaRX3(BO3)4, whereR3+=Y3+orGd3+andX3+=Al3+orSc3+. Measurements of the optical absorption spectra have been used to estimate the crystal field strengthDqand the Racah parametersBandC. These quantities confirm that inYAl3(BO3)4(YAB) andGdAl3(BO3)4(GAB)Cr3+ions occupy strong crystal field sites2E)<E(4T2)], whereas inYSc3(BO3)4(YSB) andGdSc3(BO3)4(GSB) theCr3+ions occupy weak field sites4T2)<E(2E)]. The consequence is that the fluorescence spectrum ofCr3+:YAB and GAB reveals the sharpRlines at low temperature andRlines plus broadband at 300 K. BothCr3+:YSB and GSB emit into the broadband4T2→4A2transition at all temperatures. The potential of these materials as laser gain media is discussed. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115313

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We report extended studies on electroluminescence from molecularly thin semiconducting Langmuir–Blodgett films of quinquethiophene. The effect of the thickness of active layer and cathode electrode material has been investigated. From all these devices, greenish electroluminescence (visible in a dark room) has been observed with quantum efficiencies of the order of 10−3%. Even five or nine layers of Langmuir–Blodgett films yield the same luminance as thicker films. The electroluminescence spectrum showed a profile identical to the photo‐ luminescence spectrum. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115314

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

This study reports UV‐photoemission (UPS) measurements made on boron nitride crystals and thin films. The materials examined are commercial gradec‐BN powder and thin films of BN deposited with ion beam assisted e‐beam evaporation and laser ablation. The thin film samples examined exhibited varying amounts ofsp3(cubic) andsp2(hexagonal, amorphous) bonding as determined by FTIR measurements. The UPS measurements displayed the spectral distribution of the low energy photoemitted electrons and the total energy width of the spectra. These characteristics can be related to the electron affinity. The measurements on several of the BN powder and thin film samples revealed features in the emission spectra which are indicative of a negative electron affinity (NEA) surface. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115315

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Pseudomorphic Si1−x−yGexCyalloy layers on Si (100) with band‐edge photoluminescence and without defect‐related luminescence have been achieved. The photoluminescence was measured from 2 to 77 K and was used to make a direct measurement of the band gap shift as a function of strain reduction as C was added. Compared to the effect of just reducing Ge content, results show that as C is added, strain is reduced more efficiently than the band gap is increased. Furthermore, results imply that a fully strain‐compensated Si1−x−yGexCylayer on Si (100) would have a band gap much less than that of Si, and suggest that initial C incorporation reduces the band gap of relaxed, unstrained Si1−x−yGexCyalloys. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115316

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have fabricated and operated two cantilevers in parallel in a new mode for imaging with the atomic force microscope (AFM). The cantilevers contain both an integrated piezoresistive silicon sensor and an integrated piezoelectric zinc oxide (ZnO) actuator. The integration of sensor and actuator on a single cantilever allows us to simultaneously record two independent AFM images in the constant force mode. The ZnO actuator provides over 4 &mgr;m of deflection at low frequencies (dc) and over 30 &mgr;m deflection at the first resonant frequency. The piezoresistive element is used to detect the strain and provide the feedback signal for the ZnO actuator. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115317

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have measured the resonant tunneling current–voltageI(V) characteristics of strainedp‐Si/Si1−xGexdouble‐barrier microstructures ranging from 1.0 to 0.1 &mgr;m in lateral extent. The bias spacing between resonant current peaks in theI(V) reflects the energy separation of the Si1−xGexquantum well subbands, which is partially determined by the strain. As the lateral size of the structures decreases, we observe consistent shifts in theI(V) peak spacing corresponding to strain energy relaxation of ∼30% in smaller structures. An additionalI(V) fine structure is observed in the 0.1 &mgr;m device, consistent with lateral quantization due to nonuniform strain. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115318

出版商:AIP    

年代:1995

数据来源: AIP