High-Performance Two-Dimensional Electronics with a Noncontact Remote Doping Method.

Because of the intrinsic low carrier density of monolayer two-dimensional (2D) materials, doping is crucial for the performance of underlap top-gated 2D devices. However, wet etching of a high-k (dielectric constant) dielectric layer is difficult to implement without causing performance deterioration on the devices; therefore, finding a suitable spacer doping technique for 2D devices is indispensable. In this study, we developed a remote doping (RD) method in which defective SiOx can remotely dope the underlying high-k capped 2D regions without directly contacting these materials. This method achieved a doping density as high as 1.4 × 1013 cm-2 without reducing the mobility of the doped materials; after 1 month, the doping concentration remained as high as 1.2 × 1013 cm-2. Defective SiOx can be used to dope most popular 2D transition-metal dichalcogenides. The low-k properties of SiOx render it ideal for spacer doping, which is very attractive from the perspective of circuit operation. In our experiments, MoS2 and WS2 underlap top-gate devices exhibited 10× and 200× increases in their on-currents, respectively, after being doped with SiOx. These results indicate that SiOx doping can be conducted to manufacture high-performance 2D devices.

Statistical Assessment of High-Performance Scaled Double-Gate Transistors from Monolayer WS2.

Scaling of monolayer transition metal dichalcogenide (TMD) field-effect transistors (FETs) is an important step toward evaluating the application space of TMD materials. Although some work on ultrashort channel monolayer (ML) TMD FETs has been published, there exist no comprehensive studies that assess their performance in a statistically relevant manner, providing critical insights into the impact of the device geometry. Part of the reason for the absence of such a study is the substantial variability of TMD devices when processes are not carefully controlled. In this work, we show a statistical study of ultrashort channel double-gated ML WS2 FETs exhibiting excellent device performance and limited device-to-device variations. From a detailed analysis of cross-sectional scanning transmission electron microscopy (STEM) images and careful technology computer aided design (TCAD) simulations, we evaluated, in particular, an unexpected deterioration of the subthreshold characteristics for our shortest devices. Two potential candidates for the observed behavior were identified, i.e., buckling of the TMD on the substrate and loss of gate control due to the source geometry and the high-k dielectric between the metal gate and the metal source electrode.

Mobility Extraction in 2D Transition Metal Dichalcogenide Devices-Avoiding Contact Resistance Implicated Overestimation.

Schottky barrier (SB) transistors operate distinctly different from conventional metal-oxide semiconductor field-effect transistors, in a unique way that the gate impacts the carrier injection from the metal source/drain contacts into the channel region. While it has been long recognized that this can have severe implications for device characteristics in the subthreshold region, impacts of contact gating of SB in the on-state of the devices, which affects evaluation of intrinsic channel properties, have been yet comprehensively studied. Due to the fact that contact resistance (RC ) is always gate-dependent in a typical back-gated device structure, the traditional approach of deriving field-effect mobility from the maximum transconductance (gm ) is in principle not correct and can even overestimate the mobility. In addition, an exhibition of two different threshold voltages for the channel and the contact region leads to another layer of complexity in determining the true carrier concentration calculated from Q = COX * (VG -VTH ). Through a detailed experimental analysis, the effect of different effective oxide thicknesses, distinct SB heights, and doping-induced reductions in the SB width are carefully evaluated to gain a better understanding of their impact on important device metrics.

Direct observation of valley-coupled topological current in MoS2.

The valley degree of freedom of electrons in two-dimensional transition metal dichalcogenides has been extensively studied by theory (1-4), optical (5-9), and optoelectronic (10-13) experiments. However, generation and detection of pure valley current without relying on optical selection have not yet been demonstrated in these materials. Here, we report that valley current can be electrically induced and detected through the valley Hall effect and inverse valley Hall effect, respectively, in monolayer molybdenum disulfide. We compare temperature and channel length dependence of nonlocal electrical signals in monolayer and multilayer samples to distinguish the valley Hall effect from classical ohmic contributions. Notably, valley transport is observed over a distance of 4 µm in monolayer samples at room temperature. Our findings will enable a new generation of electronic devices using the valley degree of freedom, which can be used for future novel valleytronic applications.

Idiopathic cervical fibrosis--a new member of IgG4-related sclerosing diseases: report of 4 cases, 1 complicated by composite lymphoma.

Idiopathic cervical fibrosis is a rare tumefactive inflammatory-sclerosing lesion involving the soft tissues of the head and neck, and a proportion of patients also have synchronous or metachronous inflammatory fibrosclerosing lesions in other anatomic sites. The latter finding suggests that this entity may represent a member of IgG4-related sclerosing diseases. We report 4 cases to support this postulation. The patients were male adults aged 42 to 89 years, who presented with an infiltrative, firm cervical mass. Two patients also had IgG4-related chronic sclerosing sialadenitis of submandibular gland and lymphadenopathy. Histologically, the cervical soft tissue lesions had ill-defined borders, consisting of coalescent nodular lymphoid aggregates accompanied by a sclerotic stroma. Nerve infiltration, skeletal muscle invasion, and phlebitis were present. There was a significant increase in IgG4 plasma cells (87 to 327 per high-power field, with IgG4/IgG ratio of 63% to 98%). In the soft tissue lesion of 1 patient, there were expansile foci comprising dense sheets of plasma cells and small lymphoid cells that exhibited κ light chain restriction and clonal immunoglobulin gene rearrangement, consistent with supervening extranodal marginal zone lymphoma. The adjacent lymph node from the same patient showed Epstein-Barr virus (EBV)-positive classical Hodgkin lymphoma with typical morphology and immunophenotype (CD30, CD15, PAX5). Thus lymphoma can supervene in the chronic inflammatory background similar to that recently documented for IgG4-related sclerosing disease of the ocular adnexa.

Nasopharyngectomy: does the approach to the nasopharynx influence survival?

OBJECTIVE: To investigate whether the approach used to the nasopharynx to perform a salvage nasopharyngectomy for recurrent or residual nasopharyngeal carcinoma influences survival. STUDY DESIGN: A retrospective case series. SUBJECTS AND METHODS: Eighty patients underwent a nasopharyngectomy via a transpalatal, maxillary swing, or midfacial degloving approach. Local progression-free, locoregional progression-free, and overall survival rates were calculated for each approach. RESULTS: For the whole group (N = 80), there were no significant differences in the survival rates between the three approaches. For the subgroup of patients with recurrent T1 and T2 tumors (n = 68), the local progression-free and locoregional progression-free survival rates were significantly better when a maxillary swing approach was used than when a midfacial degloving approach was used. CONCLUSION: The maxillary swing approach is associated with significantly better survival rates than the midfacial degloving approach when used to perform a salvage nasopharyngectomy for residual or recurrent T1 and T2 nasopharyngeal carcinoma.

The development of Cantonese Lexical Neighborhood Test: a pilot study.

OBJECTIVE: This study aimed at developing a theoretically driven open-set speech recognition test for pediatric clinical population of cochlear implant and/or hearing aid users, with Cantonese Chinese as their first language, to track progress in speech recognition performance as an outcome measurement of their rehabilitation. METHODS: Six monosyllabic and six disyllabic word lists were generated from the Cantonese CHILDES language database, constructed according to the Neighborhood Activation Model. There were three lexically "easy" and three lexically "hard" word lists in each sub-test, with 25 items in each list. Four pediatric cochlear implant users and 10 hearing aid users, with bilateral congenital severe to profound sensorineural hearing impairment and below the age of 10, participated in the study. Their performances on word recognition and phoneme recognition with the new test lists, as well as the inter-list equivalency, inter-rater reliability, and face validity of the new materials, were investigated. RESULTS: Word recognition was higher among disyllables than monosyllables. Lexically "easy" disyllabic words were better recognized than their "hard" counterparts and the monosyllables. No significant difference was noted among the three lists in each combination of syllable structure and lexical property. High inter-rater reliability, as well as high correlation between Cantonese LNT score and a receptive vocabulary test score, were revealed. CONCLUSIONS: These newly developed test lists provided reliable information on spoken word recognition of pediatric hearing prosthesis users with severe to profound hearing impairment. Inter-list equivalency and inter-rater reliability allowed monitoring of rehabilitation progress on such specific pediatric clinical population with this new test. (255).

The frontal bone skull post for image guided surgery of the nasopharynx.

BACKGROUND AND OBJECTIVES: To describe the use of the mastoid skull post of a surgical image guidance system for image guided surgery and intraoperative navigation of the nasopharynx. This adaptation overcomes the limitations of a headset frame or head clamp and can be applied to open and closed surgery of the nasal cavities, sinuses, orbits, midface and anterior skull base. METHODS: A sterile mastoid skull post of a surgical image guidance system was securely screwed into the outer table of the frontal bone and a passive reference frame fixed to it. The position of the reference frame relative to the patient's head remained constant during surgery. RESULTS: Between August 2002 and November 2006, 22 patients underwent a surgical nasopharyngectomy using an image guidance system and frontal bone skull post. No surgical complications or complications of the frontal bone skull post occurred. CONCLUSION: Using the skull post of a surgical image guidance system anchored to the frontal bone to carry a passive reference frame provides real-time visual information about the relationship of relevant anatomy to the surgical field on a fully mobile head in open or closed procedures of the midface and anterior skull base while accuracy and sterility are maintained.

Long-term outcome of the Hong Kong vascularized, pedicled temporalis fascia flap in reconstruction of mastoid cavity.

OBJECTIVES: The vascularized, pedicled temporalis fascia flap (Hong Kong flap) is an established procedure in the reconstruction of the mastoid cavity. The long-term outcome and complications have not been studied. We set out to appraise this procedure in our study. STUDY DESIGN: The clinical records of 302 ears that had the Hong Kong flap procedure from 1987 to 2006 were retrospectively studied. The study reviewed the otologic complaints leading to Hong Kong flap, the number and findings of the second or more looks, analysis of procedures year by year, time to achieve a dry ear, and the complications. RESULTS: The main otologic complaint leading to use of the Hong Kong flap is otorrhoea. The number of Hong Kong flap procedures has decreased in recent years. Twenty-one percent had second or more looks after the procedure. Forty percent of the mastoid cavities at the second look were found to have residual or recurrent cholesteatoma. It takes a median of 2 months to achieve a dry ear after the procedure. CONCLUSIONS: We conclude that the Hong Kong flap procedure is simple and desirable for mastoid reconstruction to achieve a safe and dry cavity with few complications.

Patient satisfaction after closed reduction of nasal fractures.

OBJECTIVE: To evaluate the outcome of closed reduction from a patient's point of view, because there is increasing evidence that closed reduction of nasal fractures fails to address deformities of the cartilaginous nasal framework and the septum. METHODS: We performed a retrospective study of 62 patients who underwent a closed reduction of nasal fracture between July 1, 2002, and June 30, 2005. All patients were interviewed regarding the esthetic and functional outcomes after closed reduction. RESULTS: Eighteen patients (29%) expressed dissatisfaction with the esthetic outcome of the reduction, and 18 (29%) said they would consider further surgery to correct the residual nasal deformity. CONCLUSIONS: A stringent preoperative assessment of the nasal fracture, other nasal deformities, and nasal function is essential before offering patients a simple closed reduction of their nasal fractures. A septorhinoplasty, as the definitive procedure, should be offered to patients when a closed reduction is deemed unable to address all deformities.

Visibility of puncture sites after external osteotomy in rhinoplastic surgery.

BACKGROUND: External lateral osteotomy performed through a small puncture incision in the skin has numerous advantages, but it has been criticized by its opponents who claim it may leave visible scars. OBJECTIVE: To examine whether the external lateral osteotomy actually leaves visible scars. METHODS: Eighty-one postoperative photographs of patients who had undergone the external lateral osteotomy technique were reviewed. The photographic slides were a mixture of some taken 3 months after surgery and others taken 6 months after surgery. Scar visibility was assessed. RESULTS: Percutaneous puncture site visibility as assessed by 3 surgeons independently was 0% at 6 months after surgery and about 3% at 3 months after surgery. CONCLUSION: The external osteotomy procedure produces an excellent cosmetic result at the puncture sites in the skin.

Comparison of bipolar scissors and bipolar forceps in tonsillectomy.

Bipolar diathermy scissors tonsillectomy is a relatively new surgical technique. We conducted a prospective study of 90 patients to compare this technique with bipolar forceps tonsillectomy. We found that the use of the bipolar scissors required significantly less operating time (mean: 3.03 min less) and allowed patients to resume eating solid food more rapidly (mean: 40.35 min earlier). Bipolar scissors tonsillectomy was safe, and there were no intraoperative complications or primary hemorrhages. A postoperative follow-up telephone survey revealed that patients who underwent scissors tonsillectomy experienced no more morbidity than did the forceps group during the first 2 weeks after surgery. We conclude that bipolar scissors tonsillectomy is a safe and rapid technique that can be used successfully as an outpatient procedure.