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X-ray diffraction (XRD) data shows lattice planes with a spacing of 12.8 A for copper phthalocyanine (CuPc) thin films. Comparison between the XRD patterns of CuPc powder and thin films suggests that the molecules are oriented along the (100) lattice plane nearly perpendicular to the substrate. The XRD data of the perfluorinated phthalocyanine (F16CuPc) thin film indicate a similar structure to that of CuPc, but with a wider lattice spacing of 14.6 A. Angular variations of the line position (g-value) of ESR spectra reveal tilt angles of 39 and 34° for the CuPc and F16CuPc thin films, respectively, and the same deviation angle of 24°. This indicates a cone-shaped orientation of CuPc and F16CuPc with similar tilt and deviation angles. The ESR linewidths of both films show angular variation, indicating one-dimensional spin-chain interactions in both the CuPc and F16CuPc thin films. Organic thin-film transistors (OTFTs) with CuPc and F16CuPc films are tested for their suitability as channel layers. The OTFTs with a CuPc film exhibit conduction with holes as carriers, and have a field-effect mobility of 2.6 ×10-5 cm2 V-1 s-1 and an on/off ratio of 10 in the accumulation mode. The OTFTs with F16CuPc films exhibit conduction with electrons as carriers (n-type), and have a field-effect mobility of 2.0 ×10-4 cm2 V-1 s-1 and an on/off ratio of 2.4 ×104 in the accumulation mode.

Titanium-containing alkoxide (Ti[i-OCH(CH3)2]4) dissolved in 2-methoxyethanol was directly deposited onto silicon by the metalorganic decomposition (MOD) technique. Titanium oxide (TiO2) thin films are formed uniformly on Si after high-temperature annealing. Raman and X-ray diffraction measurements indicate that the structure changes completely from anatase to rutile phase at an annealing temperature of 700°C. During the crystallization, however, the reaction starts at the TiO2/Si interface, resulting in the formation of interfacial SiO2 layer with a thickness of 2.6 nm. In contrast, the TiO2 thickness was fairly constant. The capacitance-voltage characteristics revealed that with annealing temperature, the dielectric constant increases to a maximum (emax=48) at 700°C. However, the dielectric constant decreases again above 700°C due to the occurrence of interfacial SiO2 growth. For the well crystallized TiO2 films, the leakage current decreases to 7×10-8 A/cm2 at 2 MV/cm and the maximum breakdown field is 3.3 MV/cm. The TiO2 thin films formed by MOD are expected to act as a suitable dielectric in place of conventional thin SiO2 for future integrated circuits.

An investigation of threshold voltage shifts in organic thin-film transistors (OTFTs) based on poly[N,N '-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-bithiophene) [P(NDI2OD-T2)] with additional poly(3-hexylthiophene) (P3HT) films on a poly(methyl methacrylate) (PMMA) organic dielectric layer is reported. With a top source-drain contact structure, the device exhibited a unipolar property with n-channel characteristics similar to those of the P(NDI2OD-T2)-only device. Furthermore, the existence of P3HT films as hole acceptor-like storage layers resulted in reversible V th shift upon the application of external gate bias (V bias) for a certain bias time (T bias). Hence, the P(NDI2OD-T2)/P3HT-OTFTs exhibited a large memory window (ΔV th = 10.7 V) for write and erase electrically without major degradation in saturation mobility [µsat = (1.8–2.8) ×10-4 cm2 V-1 s-1]. These results clearly indicate the utility of the naphthalene–bis(dicarboximide) (NDI)-based polymer–hole acceptor layer in the development of n-channel organic transistor memories.

An investigation of threshold voltage shifts in organic thin-film transistors (TFTs) based on pentacene with an additional soluble fullerene derivatives of [6,6]-phenyl C61-butyric acid methyl ester (PCBM) on gate dielectric. With an additional soluble fullerene layer, the threshold voltage (V th) is optimized from -3.9 to -1.1 V without affect the mode operation of the devices, while retaining the carrier mobility (0.02–0.03 cm2 V-1 s-1) and on/off current ratio (∼104). Furthermore, the existence of PCBM agglomerates as electron acceptor-like traps resulted in a shift of V th in the positive and reversible directions depending on the magnitude of gate bias (V bias) as well as duration of time bias (T bias). The device operation changed into normally-on (depletion–accumulation) mode upon positive V bias as the duration of T bias was increased, which attributes to the formation of a conductive layer at the pentacene–fullerene interface. Moreover, the recovery of V th was further enhanced by a high negative V bias for a short duration. In addition, the mobility was minimally affected by both V bias conditions.

Zinc oxide (ZnO) thin-film transistors (TFTs) were fabricated by thermal chemical vapor deposition (CVD) using aqueous solutions of zinc acetate (ZnAc2) dihydrate as a source. The precursor was supplied to the substrate by the nitrogen bubbling method through a plate with numerous orifices in the ZnAc2 solution. The ZnO thin films were grown on silicon substrates in the growth temperature (T G) range from 280 to 700 °C. The growth rate of ZnO thin films were linearly proportional to the growth temperature, which suggested that the growth rate is limited by the decomposition of ZnAc2. Depletion-mode TFTs with the ZnO film grown at T G = 350 °C was found to exhibit a relatively low saturation mobility (µsat). However, µsat increased from 1 to 14 cm2·V-1·s-1 and the operational mode was changed from the depletion mode to the enhancement mode by annealing treatment at 200 °C for 2 h under N2 ambient.

Organic thin-film transistors (OTFTs) incorporating blends of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) as an active layer were fabricated, and the photoresponse and memory effects of the P3HT/PCBM-TFTs were investigated. With top source–drain contact, the device exhibited a unipolar property with p-channel characteristics in dark condition. Upon illumination, a significant increase in the drain current was observed, and the transfer curve was shifted in the positive direction with ΔV th = 15.5 V. Moreover, the drain current increased gradually with the response time of light illumination, while it decreased gradually with delay time after turning off the light illumination. The memory effects of the P3HT/PCBM-TFTs were attributed to the slow relaxation of photoinduced charge carriers and the electron trapping–detrapping mechanism. The memory functions of program and erase can be performed using a combination of the optical response and gate voltages.

Focused on the relationship between the molecular orientation and the electrical performance of poly(3-hexylthiophene)/[6,6]-phenyl C61-butyric acid methyl ester (P3HT/PCBM) composite thin films to elucidate the effect of changing amount of PCBM in P3HT:PCBM by weight ratio in organic solution has been studies. The P3HT/PCBM composite thin films were investigated by an electron spin resonance (ESR) and X-ray diffraction (XRD) to reveal the film molecular and structure orientation. It was observed that the composite films with a small amount of PCBM were capable of altering the molecular structure of P3HT. It was also observed that the presence of a small amount of PCBM molecules improved the device performance of P3HT thin film transistors (TFTs), which provide the mobility on the order of 10-3 cm2 V-1 s-1 with an on/off current ratio of 10-4. The threshold voltage was also higher than of pure P3HT TFTs.

Ultrathin silicon oxynitride films are prepared by ozone and thermal oxidation of Si(001) followed by rapid thermal nitridation. The nitrogen depth profiles in these films are measured by high-resolution Rutherford backscattering spectroscopy. The observed nitrogen profiles are essentially similar, having a peak at the SiO2/Si interface, although the interface strain in the ozone oxide is known to be much smaller than that of the thermal oxide. This indicates that the interface strain relaxation due to the nitrogen incorporation is not responsible for the nitrogen accumulation at the interface.

A novel device based on a porous Pt–WO3 metal-insulator-semiconductor field-effect transistor (MISFET) for carbon monoxide (CO) gas sensing has been fabricated. The structure integrates the catalytic properties of porous Pt as a thin catalytic layer, and the spillover effect onto WO3 film as a gas adsorptive oxide layer, with surface-sensitive MISFET. The operation characteristics of the device for the detection of CO gas are presented as a function of CO gas concentration. The drain current increased rapidly with time depending on the CO gas concentration. It was possible to detect 54 ppm of CO gas with a response time of less than 1 min at 75°C. A model was proposed to explain the operation. The sensing mechanism of the device is supported well by experimental data.

Polycrystalline (1-x)Ta2O5–xTiO2 thin films were formed on a Si substrate by metalorganic decomposition (MOD) at an annealing temperature of 900°C. Thin films with 0.92Ta2O5–0.08TiO2 (x=0.08) composition exhibited superior insulating properties compared to other compositions. The main reason for the improvement in the insulating properties could be the charge compensation of excess oxygen by the TiO2 additive. The leakage current density was lower than 1×10-9A/cm2 up to an applied electric field of 3 MV/cm. The bulk-limited Poole-Frenkel conduction dominates the current–voltage characteristics. capacitance–voltage characteristics of these films showed good dielectric properties with a maximum dielectric constant of 16 and a charge-storage density of 42.5 fC/µm2 at 3 MV/cm.

Titanium oxide (TiO2) thin films were formed on a Si substrate by metalorganic decomposition at temperatures ranging from 600°C to 1000°C. As-deposited films were in the amorphous state and were completely transformed after annealing at 600°C to a crystalline structure with anatase as its main component. During crystallization in oxygen atomosphere, a reaction between TiO2 and Si occurred at the interface, which resulted in the formation of a thin interfacial SiO2 layer. Capacitance-voltage measurement showed good dielectric properties with a maximum dielectric constant of 76 for films annealed at 700°C. For the crystallized TiO2 films, the interface trap density was 1×1011 cm-2eV-1, and the leakage current was 1×10-8 A/cm2 at 0.2 MV/cm. The modified structure of TiO2/SiO2/Si is expected to be suitable for the dielectric layer in an integrated circuit in place of SiO2 or Si3N4 films.

Novel gas-sensing devices based on a porous Pt-SnO2 metal-oxide-semiconductor field-effect transistor (MOSFET) for carbon monoxide (CO) gas sensing have been fabricated. The structure integrates the catalytic properties of porous Pt, a thin catalytic layer, and the spillover effect onto SnO2, a gas adsorptive oxide, with surface-sensitive MOSFETs. The operation characteristics of the device for the detection of CO are presented as a function of CO gas concentration and operating temperature. The threshold voltage decreased rapidly with time when the device was exposed to CO gas. It was possible to detect 54 ppm of CO gas with a response time of less than 1 min at an operating temperature of 27°C. A model was proposed to explain the operation. The proposed sensing mechanism of the device is supported well by experimental data.

Crystalline CeO2 films were formed on a Si (100) substrate by metalorganic decomposition at temparatures ranging from 600°C to 800°C. As-deposited films were in the amorphous state and were completely transformed to crystalline CeO2 above 600°C. However, during crystallization in oxygen atomosphere, a reaction between CeO2 and Si occurred at the interface, which resulted in the formation of a thin interfacial SiO2 layer. Capacitance-voltage measurement on these films showed good dielectric properties with a dielectric constant of 15, which is more than three times higher than that of SiO2. The modified structure of CeO2/SiO2/Si is expected to be suitable for the dielectric layer in an integrated circuit, in place of conventional dielectric films such as those of SiO2 or Si3N4.

Novel gas-sensing devices based on a porous platinum (Pt) gate metal-oxide-semiconductor field-effect transistor (MOSFET) have been fabricated. The catalytic properties of the porous Pt surface for hydrogen (H2) enhance the gas detection sensitivity of the MOSFET gas sensor. The threshold voltage decreased rapidly with time when the device was exposed to H2 gas. It was possible to detect 22 ppm of H2 gas with a response time of less than 2 min at a device temperature of 27°C. The gas sensitivity could be enhanced to about 10 times higher than that of an unmodified Pt surface. The device detection mechanism presented corresponds well with the experimental data.

A larger charge-to-breakdown value and much less threshold-voltage narrowing in the endurance properties of flash electrically erasable and programmable ROMs were achieved by incorporating a greater amount of nitrogen ( ∼1021 atoms/cm3) into the bulk of thin oxide films, as well as near the oxide/Si interface. The charge to breakdown value of thin oxide films formed under an optimized heavy oxynitride condition (dry oxidation at 1100° C; NH3 annealing at 1000° C for 30 s; N2O annealing at 1100° C for 30 s) was four times as large as that of a conventional dry oxide film. These results were attributed to the suppression of stress-induced charge traps and the interface state, due to the introduction of nitrogen atoms in the oxide bulk, as well as at the oxide/Si interface.

Charge trapping properties of ultrathin rapid thermal N2O-oxynitrided (RTON) SiO2 film have been investigated by Fowler-Nordheim (F-N) electron injection. By applying F-N stress, gate voltage decreases at the initial stage and then increases with increasing injected charge. A model of trap filling and trap generation in the oxide films indicates that the RTON film has a one order of magnitude smaller trap generation rate compared with pure SiO2 film.

Anneal kinetics of the SiO2/Si(100) interface defects of 5-nm-thick SiO2 films have been investigated through comparison of the electron spin resonance (ESR) center with the interface trap density D i t . The ESR signal showed two distinct defects (so-called Pb0 and Pb1) at the SiO2/Si(100) interface: These Pb0 and Pb1 defects are annihilated by a low-temperature (500°C) deuterium (D2) anneal. By contrast, the D2 anneal at 900°C causes an increase in the number of the defects after a decrease at the initial stage (< 10 s). We conclude that there are annihilation and dissociation processes causing the Pb0 and Pb1 defects, dependent on the D2 anneal time and temperature.

We have proposed a novel single-step rapid thermal oxynitridation (SS-RTON) technology to obtain highly reliable ultrathin electrically erasable programmable read-only memory (EEPROM) tunnel oxide films. The SS-RTON process can be achieved by rapid switching of the ambient gases (O2→N2O) at the midpoint of the oxidation period, while maintaining the oxidation temperature. The results indicate almost no increase in the oxide-trap-assisted leakage and/or in the electron trap density, resulting in the increase of the charge-to-breakdown value. This behavior of the SS-RTON film can be explained by the idea that the trap sites are reduced by forming strong Si-N bonds in bulk SiO2.

We have proposed, for the first time, a practical model for ultrathin (2 film growth in rapid thermal oxidation (RTO) kinetics. The results showed that the overall RTO growth can be well described by the linear-parabolic model proposed by Deal and Grove [J. Appl. Phys. 36 (1965) 3770]. Moreover, the model proposed indicates that in order to fit the experimental data, the oxide growth in a ramp-up process must be included in the linear-parabolic scheme. As a result, we have succeeded in explaining the RTO growth kinetics in the RTO temperature range from 950 to 1200°C and in a wide thickness range from 15 to 250 Å without making any special assumptions. The resultant activation energies for the linear rate constant (B/A) and for the parabolic rate constant (B) are 2.0 eV and 1.74 eV, respectively.

Dielectric and physical properties of N2O-oxynitrided (RTON) ultrathin (5-10 nm) SiO2 films formed by in situ multiple rapid thermal processing have been investigated. In high-field stressing under positive and negative polarity biases, the RTON SiO2 films showed a much lower electron-trap generation rate, a lower field-induced leakage current and a higher charge-to-breakdown value, as compared to those of pure SiO2 and rapid thermally NH3-nitrided (RTN) SiO2 films. Fourier transform-infrared reflection attenuated total reflectance (FT-IR ATR) and X-ray photoelectron spectroscopy (XPS) results showed that strong Si-N bonds are formed at the SiO2/Si interface by RTON, whereas a large number of N-H and Si-H bonds, which act as electron traps, are also generated by RTN.

A novel method of nitridation of thin SiO2 film (in situ multiple rapid thermal processing (RTP) using oxygen (O2) and nitrous oxide (N2O) as reactants. Nitrided SiO2 (SiO x N y ) films, in which nitrogen piles up about 5 at% at the SiO x N y /Si interface, showed smaller densities of electron and hole traps in high-field stressing as compared to those of pure SiO2 films. However, only the SiO x N y film formed via oxidation in O2 and following nitridation in N2O ambients has a large charge-to-breakdown value (>30 C/cm2) and indicates a quite uniform interface ordered within at least one or two atomic layers.

Very thin SiO2 films, 3–10 nm in thickness, have been formed on silicon by rapid thermal processing (RTP), and their dielectric reliability has been investigated in comparison with furnace-grown oxides. The SiO2 films grown by RTP are superior to furnace oxides on both the dielectric breakdown and the Si-SiO2 interface characteristics. On the RTP SiO2 films, quantum oscillation in MOS tunneling is clearly observed at 300 K. The Si-SiO2 interface roughness is estimated from the Fowler-Nordheim plot. These results indicate that the Si-SiO2 structure is ordered within one monolayer.

Amorphous carbon films were prepared by the glow-discharge decomposition of C2H2, C2H4, and C2F6 at various rf powers and substrate temperatures (T s). The deposition rate (DR) of a-C:H and a-C:H:F decreases with increase in T s. These results are discussed in terms of the H-plasma etching of a-C:H films during the deposition. The optical, electrical and structural properties of the a-C:H films are also examined as a function of the rf power.