Structural and Electrical Characterization of SiO2 Gate Dielectrics Deposited from Solutions at Moderate Temperatures in Air.

Silicon dioxide (SiO2) is the most widely used dielectric for electronic applications. It is usually produced by thermal oxidation of silicon or by using a wide range of vacuum-based techniques. By default, the growth of SiO2 by thermal oxidation of silicon requires the use of Si substrates whereas the other deposition techniques either produce low quality or poor interface material and mostly require high deposition or annealing temperatures. Recent investigations therefore have focused on the development of alternative deposition paradigms based on solutions. Here, we report the deposition of SiO2 thin film dielectrics deposited by spray pyrolysis in air at moderate temperatures of ≈350 °C from pentane-2,4-dione solutions of SiCl4. SiO2 dielectrics were investigated by means of UV-vis absorption spectroscopy, spectroscopic ellipsometry, XPS, XRD, UFM/AFM, admittance spectroscopy, and field-effect measurements. Data analysis reveals smooth (RRMS < 1 nm) amorphous films with a dielectric constant of about 3.8, an optical band gap of ≈8.1 eV, leakage current densities in the order of ≈10-7 A/cm2 at 1 MV/cm, and high dielectric strength in excess of 5 MV/cm. XPS measurements confirm the SiO2 stoichiometry and FTIR spectra reveal features related to SiO2 only. Thin film transistors implementing spray-coated SiO2 gate dielectrics and C60 and pentacene semiconducting channels exhibit excellent transport characteristics, i.e., negligible hysteresis, low leakage currents, high on/off current modulation ratio on the order of 106, and high carrier mobility.

ZnO-based thin film transistors employing aluminum titanate gate dielectrics deposited by spray pyrolysis at ambient air.

The replacement of SiO2 gate dielectrics with metal oxides of higher dielectric constant has led to the investigation of a wide range of materials with superior properties compared with SiO2. Despite their attractive properties, these high-k dielectrics are usually manufactured using costly vacuum-based techniques. To overcome this bottleneck, research has focused on the development of alternative deposition methods based on solution-processable metal oxides. Here we report the application of spray pyrolysis for the deposition and investigation of Al2x-1·TixOy dielectrics as a function of the [Ti(4+)]/[Ti(4+)+2·Al(3+)] ratio and their implementation in thin film transistors (TFTs) employing spray-coated ZnO as the active semiconducting channels. The films are studied by UV-visible absorption spectroscopy, spectroscopic ellipsometry, impedance spectroscopy, atomic force microscopy, X-ray diffraction and field-effect measurements. Analyses reveal amorphous Al2x-1·TixOy dielectrics that exhibit a wide band gap (∼4.5 eV), low roughness (∼0.9 nm), high dielectric constant (k ∼ 13), Schottky pinning factor S of ∼0.44 and very low leakage currents (<5 nA/cm(2)). TFTs employing stoichiometric Al2O3·TiO2 gate dielectrics and ZnO semiconducting channels exhibit excellent electron transport characteristics with low operating voltages (∼10 V), negligible hysteresis, high on/off current modulation ratio of ∼10(6), subthreshold swing (SS) of ∼550 mV/dec and electron mobility of ∼10 cm(2) V(-1) s(-1).

Effect of type I tympanoplasty on the resonant frequency of the middle ear: comparison between chondrotympanoplasty and temporalis fascia grafting.

AIMS: To evaluate the effect of type I chondrotympanoplasty on the resonant frequency (RF) of the middle ear and compare it to the respective outcomes of type I tympanoplasty using temporalis fascia grafting (TFG). Hearing results and respective graft integration rates were also assessed. MATERIALS AND METHODS: A retrospective comparative study was conducted of patients who had undergone type I tympanoplasty at a tertiary university hospital. Selection criteria included tympanic membrane perforation following chronic otitis media, trauma, or grommet insertion; an intact ossicular chain; a dry ear for at least 3 months; and normal middle ear mucosa. Patients with ossicular discontinuity, ossiculoplasty, cholesteatoma, previous ear surgery, syndromes affecting the middle ear, or younger than 16 years old were excluded. RESULTS: Sixty-nine patients met the inclusion criteria; chondrotympanoplasty was performed in 39 and TFG in 30. Three patients showed incomplete tympanic membrane closure at follow-up. The graft integration rate was 97.4% in the chondrotympanoplasty group and 93.3% in the TFG group. An air-bone gap closure within 10 dB was achieved in 73.7% of the chondrotympanoplasty patients versus 67.9% of the TFG patients. Hearing gain of 21 to 30 dB in air conduction thresholds was obtained in 65.8% of the chondrotympanoplasty patients and 60.7% of their TFG counterparts. RF was 808 ± 458 Hz in the chondrotympanoplasty group and 628 ± 256 Hz in the TFG group. The RF remained within the normal range in 73.7% of chondrotympanoplasty patients versus 42.9% of TFG patients. CONCLUSIONS: Chondrotympanoplasty has hearing results comparable to those of TFG myringoplasty. The cartilage can be used without concerns regarding its impact on the middle ear mechanics as the sound-conducive properties of the tympanic membrane remain unchanged.

Chondrotympanoplasty: a modified technique of cartilage graft tympanoplasty.

BACKGROUND: Although the temporalis fascia has been widely used since 1957as a graft in tympanoplasty, it can eventually become thin and atrophic. In addition, due to the lack of elasticity and resistance to pressure changes in the external ear canal, secondary perforations may also develop. Therefore, several authors have suggested that temporalis fascia should be strengthened by periosteum or replaced by cartilage. MATERIAL/METHODS: In the present paper the term chondrotympanoplasty is introduced to describe modified techniques of cartilage graft tympanoplasty and intratympanal chondroplasties. These techniques were used in 76 patients who were prospectively followed up for two years post-operatively. RESULTS: In type I chondrotympanoplasty, the mean pre-operative air-bone gap was reduced from 20 dB to 8 dB at 2000 Hz. In 93% of these cases the cartilage graft was taken without problems and there was no perforation in the new eardrum. In two cases of type I chondrotympanoplasty who experienced acute post-operative otitis media, the cartilage graft was found to be relatively resistant to infection, as only a pinhole perforation was noted. Type III chondrotympanoplasty with endotympanic chondroplasty (intratympanal tubal chondroplasty and intratympanal stapes chondroplasty) was found to give good aeration in the cavity, an intact new eardrum, and remarkable hearing results, reducing the mean pre-operative air-bone gap from 25 dB to 10 dB at 2000 Hz. CONCLUSIONS: Cartilage was found to be an excellent graft material and the described chondrotympanoplasties gave very promising results. Cartilage should be used more widely in tympanoplasty (chondrotympanoplasty).

Partial laryngectomy after irradiation failure.

INTRODUCTION: Radiation therapy is often the first method of treating patients with early cancer of the glottis. There is a substantial failure rate among these patients. Total laryngectomy has usually been the means of treating patients with failure after radiation. In recent decades, partial laryngectomy has been used for salvage in such patients. This article will discuss the use of partial laryngectomy for radiation failure both from the oncologic result as well as the morbidity. PATIENTS AND METHODS: Between 1984 and 1995, 27 patients with early-stage laryngeal carcinoma underwent salvage partial laryngectomy after irradiation failure. Vertical laryngectomy was performed in 18 patients (13 with T1 N0 and 5 with T2 N0) and horizontal-supraglottic laryngectomy in 9 patients (3 with T1 N0, 1 with T2 N0, and 5 with T2 N1). The mean follow-up was 4.1 years. RESULTS: Local control was obtained in 77.7% of patients with glottic lesions (T1: 84.6%; T2: 60%, P = NS) and in 55.5% of patients with supraglottic lesions (T1: 66.6%; T2: 50%; P = NS). There was no regional recurrence in the vertical laryngectomy group, whereas the regional control rate in the horizontal-supraglottic laryngectomy group was 77.7%. Distant control was achieved in 94.4% of patients with glottic disease and in 77.7% of patients with supraglottic disease. The overall survival rate for glottic lesions was 88.8% (T1: 92.3%; T2: 80%; P = NS) versus 66.6% for supraglottic lesions (T1: 100%; T2: 50%; P = NS). CONCLUSION AND SIGNIFICANCE: Vertical laryngectomy was not associated with an increased complication rate. Morbidity in the horizontal-supraglottic laryngectomy group was higher, but a satisfactory functional outcome was obtained in all cases. Therefore, in early laryngeal cancer (glottic T1-T2, supraglottic T1) partial laryngectomy can be performed with good expectation of cure and satisfactory laryngeal function. In T2 supraglottic lesions, the oncologic results are less satisfactory; further research is required for developing more efficient complimentary or alternative treatments modalities.

Otoacoustic emissions for monitoring aminoglycoside-induced ototoxicity in children with cystic fibrosis.

OBJECTIVE: To investigate whether transient-evoked and distortion-product (DP) otoacoustic emissions (OAEs) are more sensitive than pure-tone audiometry (PTA) in revealing gentamicin-induced ototoxicity in children with cystic fibrosis (CF). DESIGN: Prospective case-control study. SETTING: Tertiary referral audiologic center in conjunction with an academic pediatric CF unit. PARTICIPANTS: The study group consisted of a consecutive sample of 12 audiologically normal children with CF and a history of gentamicin exposure (CF-gentamicin group). The control groups consisted of 8 age-matched children with CF and 11 age-matched healthy volunteers. No member of the control groups had a history of aminoglycoside exposure. INTERVENTION: Members of the CF-gentamicin study group received 4 mg/kg of gentamicin per day for a mean of 14.2 days (range, 11-29 days). OUTCOME MEASURES: The PTA thresholds (250-8000 Hz) were the criterion standard. Transient-evoked OAEs' reproducibility at 5 frequency bands (800, 1600, 2400, 3200, and 4000 Hz) and total emission level were measured, as were DP-audiogram (DP-gram) amplitude (1001-6299 Hz), input-output function dynamic range, and detection thresholds at 4004, 6006, and 7996 Hz. Baseline measurements were compared between groups examining the effect of CF and previous gentamicin exposure (2-way analysis of variance). For the CF-gentamicin group, baseline measurements were compared with those at the end of the last gentamicin treatment (paired t test). RESULTS: The PTA findings were normal for all groups at baseline and remained normal in the CF-gentamicin group after treatment. The CF-gentamicin group had significantly lower transient-evoked OAEs total emission level, DP-gram amplitude at 5042 Hz, and input-output dynamic ranges with higher detection thresholds in all frequencies compared with both control groups, which was attributed completely to previous gentamicin exposure (P<.05). After treatment, further decreases in total emission levels, DP-gram amplitudes (>3000 Hz), and dynamic ranges were noted, with increased detection thresholds (P<.05). CONCLUSIONS: Otoacoustic emissions measurement (especially of DP OAEs) proved more sensitive than PTA in revealing minor cochlear dysfunction after gentamicin exposure. They should be used for monitoring patients receiving ototoxic factors such as aminoglycosides.