Theoretical and experimental investigations of the thermoelectric properties of Al-, Bi- and Sn-doped ZnO

In this paper, the thermoelectric properties of ZnO doped with Al, Bi and Sn were investigated by combining experimental and theoretical methods. The average Seebeck coefficient of Bi doped ZnO over the measured temperature range is improved from −90 to −497 μV/K. However, segregation of Bi₂O₃ in ZnO:Bi sample, confirmed by FESEM, lead to enormous grain growth and low electrical conductivity, which makes Bi is not a good dopant to improve ZT value of ZnO. As a 4+ valence cation, Sn doping actually show an increase in carrier concentration to 10²⁰ cm⁻³, further enhancing the electrical conductivity. Unfortunately, the Seebeck coefficient of ZnO:Sn samples is even lower than pure ZnO sample, which lead to a low ZT value. As for ZnO:Al sample, with nearly no change in lattice thermal conductivity, electrical conductivity and Seebeck coefficient were both enhanced. Threefold enhancement in ZT value has been achieved in ZnO:Al sample at 760 °C compared with pure ZnO.     

Scanning spreading resistance microscopy for failure analysis of nLDMOS devices with decreased breakdown voltage

Scanning Spreading Resistance Microscopy (SSRM) is successfully applied to investigate failing nLDMOS test devices that exhibit a lowered break down voltage (BVDSS) in electrical test. Cross-sectional, two-dimensional maps of the local sample resistivity from fail and reference (pass) devices reveal significant differences of the dopant concentration in individual, specific regions. This important information enables unambiguous identification of the root cause of the device failure to be dopant related. Furthermore, from a set of hypothesis, which explains the failed electrical test, SSRM results confirm exactly one and rule out the other. These are two important steps towards root cause identification. Since a relative comparison of fail and pass SSRM scans is sufficient for this failure analysis, an extensive data calibration for the absolute dopant concentration by means of additional SSRM measurements on test samples with known dopant concentration is not required. The ability of SSRM to prove or disprove miscellaneous fail hypothesis even without data calibration makes this method a very powerful tool for analysis of dopant related failure types.     

Synthesis,identification and study of electrical conductivity of the doped copolymer carbazole–phenol formaldehyde

The copolymer carbazole–phenol formaldehyde doped with 4 (4-hydroxy-phenyl azo)-benzene sulfonic acid (PABS), 2,5-dimethyl benzene sulfonic acid (PXSA) and 4-hydroxy-m-benzene disulfonic acid (PDSA) were prepared. These compounds are identified by FT-IR spectroscopy.The conductivity of copolymer carbazole–phenol formaldehyde doped with 4 (4-hydroxy-phenyl azo)-benzene sulfonic acid (PABS), 2,5-dimethyl benzene sulfonic acid (PXSA) and 4-hydroxy-m-benzene disulfonic acid (PDSA) was studied as a function of weight of the dopant compounds; an increase of conductance of the copolymer by doping with PABS is noted; the conductance became equal to 0.000595 ohm⁻¹ for 0.1 g higher conductance for the copolymer when it is doping with PABS.     

Study on silicon surface oxidation of post-implant resist cleaning

Minimum substrate loss is required for resist strip of high dose, ultra shallow junction implant for source/drain extensions. Silicon surface oxidation of downstream plasma resist strip results in silicon recess of the source/drain extension regions. This paper reports the study of silicon surface oxidation for different resist strip plasma chemistries and the effect of plasma strip process parameters such as power, pressure and temperature on silicon surface oxidation. A good agreement was found between optical ellipsometry, XPS (X-ray photoelectron spectroscopy) and TEM (transmission electron spectroscopy) for thickness measurement of very thin (<20 Å) oxide grown on silicon surface due to plasma exposure. Selectivity of crust breakthrough and resist removal over silicon oxidation was also discussed in this paper along with dopant loss.     

Dopant segregation in SOI Schottky-barrier MOSFETs

We present experimental results on silicon-on-insulator Schottky-barrier MOSFETs with fully silicided NiSi source and drain contacts. Dopant segregation during silicidation was used to improve the device characteristics: on-currents, significantly higher than without dopant segregation as well as an almost ideal off-state are demonstrated in n-type as well as p-type SB-MOSFETs. Temperature dependent measurements show that the effective Schottky-barrier height in devices with segregation can be strongly lowered. In addition, we investigate the dopant segregation technique with simulations. Comparing simulations with experiments it turns out that the spatial extend of the segregation layer is on the few nanometer scale which is necessary for ultimately scaled devices. Furthermore, the use of ultrathin-body SOI in combination with ultrathin gate oxides results in an even further increased transmission through the Schottky barriers and consequently leads to strongly improved device characteristics. As a result, the dopant segregation technique greatly relaxes the requirement of low Schottky-barrier silicides for high performance transistor devices.     

Diffusion and doping issues in germanium

This paper gives a review on self- and dopant diffusion in germanium (Ge) under thermal equilibrium and irradiation conditions and specifies the underlying mechanisms of diffusion and the point defects involved. Diffusion in Ge under thermal equilibrium conditions is mainly controlled by vacancies. However, Ge interstitials mediate the diffusion under concurrent annealing and irradiation. This is verified by the diffusion behavior of self-atoms, boron, phosphorus and arsenic under proton irradiation. The diffusion under irradiation is explained with the property of the Ge surface that is proposed to be an insufficient sink for Ge interstitials. As a consequence, a supersaturation of self-interstitials is established during irradiation, whereas the vacancy concentration is kept at thermal equilibrium. This explains that under irradiation the diffusion of self- and dopant atoms via self-interstitials becomes visible that is otherwise negligible under conventional annealing conditions. Our findings demonstrate ways to switch between vacancy and self-interstitial mediated diffusion and shows new strategies in the diffusion doping of Ge for technological applications.     

掺杂剂对聚乙炔中电荷密度波的影响

用CNDO／2方法研究了各种掺杂剂对聚乙炔中电荷密度波的影响，在掺杂剂附近的碳原子上出现较大的电荷密度，且p型比n型掺杂剂的影响更大，讨论了电荷波与导电性的关系。     

A molecular dynamics study of ion migration in a doped electroactive polymer

Simulating the \hbox{BF}_{4}^{-} -doped poly(3-octylthiophene) lattice by molecular dynamics results in a structure in which dopant ions intercalate as a sandwich between thiophene rings on adjacent polymer chains. The ions occupy sites in channels parallel to the polymer main chain, which retains a high degree of planarity in contrast to the pristine (undoped) polymer. Even when lattice imperfections are created by expanding the cell, Coulomb forces ensure that the intercalation features containing the dopant channels are largely retained. On applying electric fields in the principal directions of the 'perfect lattice' it is found that the ions migrate most readily along the ion-channel directions (the lattice c axis), leaving the lattice undisturbed. Although higher electric fields cause dopant migration to occur perpendicular to the channel directions they destroy the intercalated lattice. In the reduced-order lattice regions substantial motion of the ions are predicted at a critical value of the lattice parameter.