Surface reaction processes in C4F8 and C5F8 plasmas for selective etching of SiO2 over photo-resist

Surface reactions induced by fluorocarbon plasmas were studied on Si substrates with SiO₂ and photo-resist overlayers using an inductively coupled plasma source. As source gases, C₄F₈ and C₅F₈ were employed to investigate their differences in the etching performance and the selectivity between SiO₂ and photo-resist. Deposition of fluorocarbon polymer was noticed in both gases by Fourier-transform infrared ellipsometric measurements when substrate bias was not applied. With the bias application, etching started on both substrate from certain threshold values of the bias voltage and the rate increased with increase of the voltage. However, in C₅F₈ plasma the increasing tendency on photo-resist was much less than on SiO₂, while in C₄F₈ plasma the difference is small. This difference is attributed to a larger deposition ability of C₅F₈ plasma with higher content of fluorine atoms in the polymer than that of C₄F₈ plasma as confirmed by X-ray photoelectron spectroscopy.     

Pyrolytic Trifluoromethylation of [76]-, [78]-, [84]-, and Aza[60]Fullerenes with Silver Trifluoroacetate; Evidence for Coordination of Fullerenes to Silver

Pyrolytic trifluoromethylation of [76], [78], [84], and aza[60]fullerenes with silver trifluoroacetate at 300°C results in extensive polyaddition of up to 18, 18, 20 and 20 CF₃ groups, respectively. In contrast to trifluoromethylation of [60]- and [70]fullerenes that give a full range of derivatives ranging upwards from C_n(CF₃)₂, [76]-, [78]-, and [84]-fullerenes only give C_n(CF₃)_6-18 derivatives, largely in the 10-12 CF₃ range; reaction with [76]fullerene is accompanied by formation of C₆₀(CF₃)₆ attributed to cage fragmentation. For aza[60]fullerene the hexa-addition level dominates, in contrast to its other reactions which give predominantly penta-addition products. All the compounds showed peaks at 1256±2 and 1180-1190 cm^-1, due to the CF₃ group, and peaks in this region are shown also by the soluble extract obtained on trifluoromethylation of nanotubes. As in trifluoromethylation of [60]- and [70]-fullerenes, the products obtained initially are involatile, attributed to formation os silver complexes; these are decomposed on subsequent solution in toluene. Mixed isomeric trifluoromethylated C₆₀F₈ derivatives viz. C₆₀F₇CF₃, C₆₀F₆(FG₃)₂, C₆₀F₅(CF₃)₃ and C₆₀F₄(CF₃)₄, and C₆₀F₄CF₃CF₂CF₃ (a C₆₀F₆ derivative) have been isolated from fluorination of [60]fullerene with MnF₃/K₂NilF₆ at 510°C.     

Test for YBJ-ARGO RPC working in avalanche mode

The measurement of YBJ-ARGO Resistive Plate Chamber (RPC), working in avalanche mode was performed. With different component of i-C₄H₁₀ in C₂H₂F₄-based gas mixtures C₂H₂F₄/i-C₄H₁₀/SF₆, the behavior of the detector with respect to the high voltage was studied. The experiment confirms that it is possible to operate YBJ-ARGO RPC in avalanche mode. The results show that with the gas mixtures containing 10% of i-C₄H₁₀ the detector achieves its optimum performance.     

碳氟感应耦合等离子体的SiO2介质刻蚀的研究

使用感应耦合等离子体技术,通过改变源气体流量比R(R=[C4F8]/{[C4F8] [Ar]})、射频源功率、自偏压等条件进行了SiO2介质刻蚀实验研究。碳氟等离子体的特征由朗谬探针和发射光谱技术来表征。结果表明,SiO2的刻蚀速率随放电源功率和射频自偏压的增大而单调上升,与R的关系则存在R=8%处的刻蚀速率峰值。C2基团的发射谱线强度随R的变化类似于SiO2刻蚀速率对R的依赖关系,对此给出了解释。在此基础上,对SiO2介质光栅进行了刻蚀。结果显示,在较大的R及自偏压等条件下,刻蚀后的槽形呈轻微的锥形图案,同时光刻胶掩膜图形出现分叉。结合扫描电镜技术对此进行了分析,认为光刻胶表面与侧面的能量传递和聚合物再沉积是导致出现上述现象的原因。     

Optical emission spectroscopy study of positive direct current bias enhanced diamond nucleation

High nucleation density and crystalline diamond films were deposited on a mirror-polished Si(100) substrate by horizontal microwave plasma chemical vapor deposition using a two step process consisting of positive direct current (dc) bias enhanced nucleation and growth. Optical emission spectroscopy was employed to investigate in situ the plasma emission characterization during positive biasing process. Emission lines from the Balmer series of atomic hydrogen, molecular hydrogen, CH, C₂, and Ar were observed in the visible and ultraviolet ranges when CH₄, H₂, and Ar were used as the reactant gases. The dependence of plasma emission spectra on the deposition parameters, such as biasing voltage, methane concentration and working pressure was investigated. The relative concentrations of neutral atomic hydrogen were estimated by using the Ar emission at 750.4 nm as an actinometer. A significant variation in the emission intensity of the radicals was measured with a change in the biasing voltage. The correlation between the spectra of some species and the quality of diamond films was studied. The results show that CH and C₂ both were important precursor in the diamond deposition, while C₂ was associated with the presence of amorphous phase in the films during positive dc biasing process.     

ISOLATION AND CHARACTERISATION OF C60(CF3)2

From the products of reactions of [60]fullerene with either K₂PtF₆ at 470 °C or AgF at 520 °C, we have isolated C₆₀(CF₃)₂, the simplest trifluoromethylfullerene, which gives a single ¹⁹F NMR line at -69.5 ppm. The HPLC retention time is less than that of C₆₀F₂ confirming the trend observed for other fluoro- vs. trifluoromethylfullerenes namely that the latter elute more rapidly. Other trifluoromethyl- containing species, C₆₀(CF₃)₄O, C₆₀F₅CF₃, C₆₀(CF₃)₄H₂, C₆₀(CF₃)₆H₂, and C₆₀(CF₃H)₃ were detected in the product mixture.     

C1 C60F16O: A Fluorofullerene Ether Having Exceptionally Long Chromatographic Retention

From the product of fluorination of [60]fullerene with K₂PtF₆ at 470 °C, we have isolated a small quantity (ca. 0.5 mg) of C₆₀F₁₆O, an oxahomofluorofullerene (ether) of exceptionally long HPLC retention time (50% greater than any other known fluorofullerene). The ¹⁹F NMR spectrum consists of 16 main lines and 8 minor ones, due to C₆₀F₁₆O (a single isomer of C₁ symmetry) and C₆₀F₁₆, respectively. The presence of the latter (absent on initial isolation) indicates this ether to be relatively unstable, confirmed by the failure to obtain an EI mass spectrum. The empirical formula was therefore determined by MALDI-TOF mass spectrometry in the negative-ion mode, the laser fluence being carefully adjusted at the threshold of ion formation, whence the only observable signal corresponded to the molecular ion of C₆₀F₁₆O. At slightly higher laser fluence, the base peak of C₆₀F₁₆O^·- is accompanied by C₆₀F₁₆^·- and C₆₀F₁₅O^·-. Two closely similar structures (of similar calculated stabilities) are fully consistent with the NMR data. Calculated dipole moments and the exceptionally long retention HPLC retention times suggest that both C₆₀F₁₆ and C₆₀F₁₆O may be dimers.     

Mass-Spectrometric Investigation of Gases Evolved from Fluorinated Multi-Walled Carbon Nanotubes at Heating

The mass-spectrometric investigation of the gases evolved from fluorinated multi-walled carbon nanotubes under heating was carried out. It was shown that in temperature interval from 20°C to 120°C the gases are composed predominantly of CO₂, CO and H₂O. Molecules of COF₂ can be finding in gas phase of products of decomposition at 120-300°C. Molecules of CF₄ and C₂F₆ realized from fluorinated nanotubes at 300-450°C.     

几种改性剂对稻草纤维/ABS复合材料挥发性有机化合物释放的影响

以稻草纤维及丙烯腈-丁二烯-苯乙烯（ABS）为原料,分别以活性炭、Al₂O₃、SiO₂为改性剂,通过混炼-模压工艺制备了稻草纤维/ABS复合材料,采用热重-质谱联用仪对复合材料的挥发性有机化合物（VOC）释放情况进行对比分析,探讨了几种改性剂对稻草纤维/ABS复合材料VOC释放的影响。研究发现:ABS及稻草纤维均能在热解过程中释放CH₂O、C₂H₄O及C₃H₄O,而C₆H₆、C₇H₈、C₈H₈等苯类及烷烃类物质的释放源则主要为ABS;活性炭的添加能够显著降低稻草纤维/ABS复合材料的VOC释放,其VOC释放总量降低了55.5%;Al₂O₃和SiO₂虽然能比较明显地降低复合材料中苯类物质的释放含量,分别降低了32.4%和30.9%,但是其中的Fe、Cu等金属杂质却能够催化醛类物质的产生,导致VOC释放总量分别增加了11.8%和235.7%。      

Halogen and Interhalogen Reactions with [60]Fullerene: Preparation and Characterization of C60C24 and C60C18F14

U.V. irradiation of a solution of [60]fullerene in carbon tetrachloride saturated with chlorine gave a yellow solid, the negative ion FAB mass spectrum of which is consistent with the presence of C₆₀Cl₂₄ When a solution of [60]fullerene in CCl₄was mixed with IF₅, a yellow solid was deposited in the denser IF₅ layer. The negative ion FAB mass spectrum of this material indicated it to be C₆₀C₁₈F₁₄ This result provides the first confirmation that halogenation of Merenes is a radical process. Fluorination of C₆₀Br₈ gave a range of fluorinated products, having a maximum fluorine content of ca. 36 fluorines per cage, and with either C₆₀F₁₈ or its mono-oxide as major species. EI mass spectrometry of the products at various temperatures indicates that the more highly fluorinated fiiilerenes are either less stable to heat, or are more volatile.     

Fabrication of SiO2 Microcantilever Using Isotropic Etching With ICP

This paper reports a new design and microfabrication process for high sensing guard-armed silicon dioxide (SiO₂ ) microcantilever sensor, which can be widely used in chemical, environmental and biomedical applications. One sensor platform consists of two SiO₂ cantilever beams as the sensing and reference elements, two connecting wings, and three guard arms. The guard arms prevent damage to the cantilever beam from collision. To efficiently release the SiO₂ cantilevers from the silicon substrate, an isotropic etch method using inductively coupled plasma (ICP) was developed. The isotropic etching with ICP system provides an advantage in good profile control and high etching rate than wet isotropic etching or conventional RIE (reactive ion etching); however, it has not been gained many attentions. In this work, the effects of chamber pressure, plasma source power, substrate power, SF₆ flow rate relating with Si etching rate, undercutting rate, and isotropic ratio were investigated and discussed. The optimum isotropic etching process achieved a 9.1 mum/min etch rate, 70% isotropic ratio, and 92% etching uniformity. The SiO₂ cantilever sensor was fabricated and the cantilever beam was successfully released using a patterned photoresist layer as an etching mask. This plasma isotropic etching release processing can be also applied to release other SiO₂ or metal suspended MEMS structures, such as bridges and membranes, with a fast etch rate and reasonable isotropic ratio.     

Theoretical Study of Decachlorocorannulene and its Congeners C20X10 and C20Z5

The electronic structure of C₂₀Cl₁₀ synthesized by arc discharge has been studied using ab initio calculation at MP2/3-21G theory level. Theoretical studies of C₂₀F₁₀ and C₂₀O₅, C₂₀S₅, C₂₀P₅ have been carried out using the same method.     

Ab initio calculation on fullerene C32 and Its Derivative

In this paper, we studied the equilibrium geometries, the electronic structures and the binding energies of fullerene C₃₂ as well as its hydrogenates and fluorides interactions by the SCF Hartree-Fock calculations using the latest version of GAMESS of ab initio programs. The fullerene C₃₂ is found to have a ¹A₂' closed-shell ground state in D_3d symmetry or a ¹E_U singlet state in D_3h symmetry. It is predicted to be easy to add some hydrogen or fluorine atoms to the C₃₂ cage and to produce a series of derivatives C₃₂H_2n,C₃₂F_2n (n=l, 3, 6), in which C₃₂H₂,C₃₂F₂ (D_3d), C₃₂H₆^a,C₃₂F₆^c(D_3h) are more stable. We suggest that this implies that the vertex of triplet pentagons of the C₃₂ cage is an activation site for addition.     

Trifluoromethylation of [60]- and [70]Fullerene in the Ionization Chamber of a Mass Spectrometer

Both [60]- and [70]fullerene react with either the Scherer radical (perfluorodiisopropylethylmethyl, C₉F₁₉), a mixture of branched perfluorononenes (C₉F₁₈, the product of hexafluoropropene trimerization), or β-fluorosulphatotetrafluoroethyldiheptafluoroisopropylmethyl radical (C₉F₁₈OSO₂F) in the ionization chamber of a mass spectrometer to give the positive parent ions of trifluoromethylation products, the reaction being accompanied by hydrogen addition. The reaction occurs at least partly on the walls of the ionization chamber, by a radical mechanism employing CF₃ radicals formed from the radical reactants both thermally and under electron impact; only the latter route occurs with the perfluorononenes.     

Hydrocarbon and Fluorocarbon Monitoring by MIS Sensors Using an Ni Catalytic Thermodestructor

An increase in the number of gases detectable by sensors based on Pd-SiO₂-Si (MIS) and Pt-LaF₃-Si₃N₄ -SiO₂-Si (MEIS) structures was achieved by the application of an external catalyst element (CE). It was shown that as a result of the decomposition of hydrocarbon and fluorocarbon molecules on a Ni coil (CE), the products detectable by metal-insulator-semiconductor (MIS) and metal-electrolyte-insulator-semiconductor (MEIS) sensors are formed. The simultaneous catalytic oxidation of hydrocarbons and their thermal decomposition result in an optimum CE temperature of about 1050 K for propane. The kinetics of the thermal decomposition of gases on Ni were investigated. The activation energy of the reaction for C₃ H₈ and the enthalpy in the case of CF₃-CCl were estimated     

磷酸处理对多孔SiO2薄膜质子导电特性和双电层薄膜晶体管性能的影响

采用等离子体增强化学气相沉积法(PECVD)制备了多孔SiO₂薄膜, 系统地研究了不同浓度磷酸处理对多孔SiO₂薄膜的质子导电特性、双电层电容和以此多孔SiO₂薄膜为栅介质的铟锌氧(IZO)双电层薄膜晶体管性能的影响。结果表明: 多孔SiO₂薄膜的质子电导率和双电层电容随磷酸浓度升高而增大, 60%浓度磷酸处理后多孔SiO₂薄膜质子电导率和双电层电容分别达到1.51×10^-4 S/cm和6.33 μF/cm²。随磷酸浓度升高, 双电层薄膜晶体管的工作电压降低, 并且, 电流开关比也变大。其中60%浓度磷酸处理后器件工作电压为1.2 V, 迁移率为20 cm²/(V·s), 电流开关比为4×10⁶。这种双电层薄膜晶体管有望应用在化学和生物传感等领域。     

MOLECULAR AND CRYSTAL STRUCTURE OF THE ADDUCTS OF C60F18 WITH AROMATIC HYDROCARBONS

The solubility of C₆₀F₁₈ in aromatic hydrocarbons, benzene, toluene, and xylenes (0.48-1.23 mg/mL), and decomposition enthalpies for the 1 : 1 and 1 : 2 complexes (31-70 kJ/mole) have been determined. The C₆₀F₁₈ molecule has near perfect C_3v symmetry, and the x-ray single-crystal structures of the C₆₀F₁₈ L complexes (L=hexamethylbenzene, o-, m-, p-xylene, and bromobenzene) are compared in terms of 12 types of C-C and four types of C-F bonds. Analysis of the packing modes in the crystals shows an influence of the size and polarity of the aromatic hydrocarbon molecule.     

多级孔Co/Al-SiO2催化剂制备及其费-托合成催化性能

多级孔硅铝材料因优异的性能而成为金属催化剂的重要载体。研究采用水热法以硝酸铝为铝源、正硅酸乙酯(TEOS)为硅源合成了Al掺杂SiO₂(Al-SiO₂)的多级孔材料, 然后采用等体积浸渍法负载钴, 制备了具有多级孔结构的 Co/Al-SiO₂催化剂。对Al-SiO₂材料的表征结果表明: 以四丙基氢氧化铵(TPAOH)为结构导向剂, 经80 ℃水热处理可以合成多级孔Al-SiO₂, 呈尺寸在30~40 nm范围的 “蠕虫状”大孔分布形态。将催化剂用于费-托合成反应, 与商业SiO₂负载的钴催化剂相比, Co/Al-SiO₂的CO转化率提高近一倍, CH₄选择性降低19.3wt%, C₂-C₄选择性降低13.3wt%, 汽油段产物(C₅-C₁₂)选择性达到53.3wt%。     

Solvates of the Fluorofullerenes C60F46 AND C60F48 with Aliphatic Hydrocarbons

The binary systems fluorofullerene - aliphatic hydrocarbon with normal structure were studied. The fluorofullerenes C₆₀F₄₈ and C₆₀F₄₈ were found to form molecular solvates with n-pentane, n-hexane, n-heptane, n-nonane, n-decane and n-undecane. Thermal gravimetry was used to estimate the mole composition of the solvates, differential scanning calorimetry - the dynamics of their decomposition and X-ray powder diffraction - the crystal structure of the solvates. The solubility of C₆₀F₄₈ in alkanes at room temperature was determined and dependence of solubility upon properties of solvates was shown.     

Investigation of a new In2O3-based selective H2 gas sensor with low power consumption

The nanometer-size In₂O₃ was synthesized via a reverse microemulsion. A new catalytic combustion-type In₂O₃-based H₂ gas sensor was developed based on the technology for fabricating the direct-heating-type sensor and a surface-modifying process. A dense SiO₂ layer near the surface of the sensor was formed by chemical vapor deposition (CVD) of hexamethyldisiloxane (HMDS). The SiO₂ layer, which acted as a molecular sieve, reduced the penetration of large molecular, such as C₂H₅OH, CH₄, i-C₄H₁₀, into the sensing layer, resulting in the improvement of selectivity to H₂. The sensitive properties and the working mechanism of the sensor were presented. The In₂O₃ nanoparticles prepared by microemulsion were characterized by transmission electron microscopy and X-ray diffraction.