Contact engineering has been the central issue in the context of high-performance field-effect transistors (FETs) made of atomic thin transition metal dichalcogenides (TMDs). Conventional metal contacts on TMDs have been made on top via a lithography process, forming a top-bonded contact scheme with an appreciable contact barrier. To provide a more efficient pathway for charge injection, an end-bonded contact scheme has been proposed, in which covalent bonds are formed between the contact metal and channel edges. Yet, little efforts have been made to realize this contact configuration. Here, we bridge this gap and demonstrate seeded growth of end-bonded contact with different TMDs by means of chemical vapor deposition (CVD). Monolayer WSe2 FETs with a CVD-grown channel and end contacts exhibit improved performance metrics, including an on-current density of 30 μA/μm, a hole mobility of 90 cm2/V·s, and a subthreshold swing of 94 mV/dec, an order of magnitude superior than those of top-contact FET counterparts that share the same channel material. A fundamental NOT logic gate constructed using top-gated and end-bonded WSe2 and MoS2 FETs is also demonstrated. Calculations using density functional theory indicate that the superior device performance stems mainly from the stronger metal–TMD hybridization and substantial gap states in the end-contact configuration.
Background Steroid cell tumors (SCTs) are very rare sex cord-stromal tumors and account only for less than 0.1% of ovarian neoplasms. SCTs might comprise diverse steroid-secreting cells; hence, the characteristic clinical features were affected by their propensity to secrete a variety of hormones rather than mass effect resulting in compression symptoms and signs. To date, ovarian SCTs have seldom been reported in children, particularly very young children; and pseudoprecocious puberty (PPP) as its unique principal manifestation should be reiterated. Case presentation We reported a 1-year-8-month-old girl presenting with rapid bilateral breast and pubic hair development within a 2-month period. Undetectable levels of LH and FSH along with excessively high estradiol after stimulation with gonadotropin-releasing hormone (GnRH), as well as a heterogeneous mass inside left ovary shown in pelvic sonography indicate isosexual PPP. Her gonadal hormones returned remarkably to the prepubertal range the day after surgery, and histology of the ovary mass demonstrated SCTs containing abundant luteinized stromal cells. Conclusion The case highlighted that SCTs causing isosexual PPP should be taken into consideration in any young children coexistent with rapidly progressive puberty given a remarkable secretion of sex hormones. This article also reviewed thoroughly relevant reported cases to enrich the clinical experience of SCTs in the pediatric group.
The coexistence of imperforate hymen and vaginal septum is rare and their ability to mimic malignant manifestations have not been frequently reported. This current case report describes a 13-year-old girl that presented with cyclic abdominal pain for 6 months. She was found to have a huge mass via abdominal plain film X-ray and sonography, with inexplicably high levels of serum carcinoembryonic antigen, cancer antigen (CA)-19-9 and CA-125. Pelvic computed tomography imaging disclosed two huge cystic lesions in the uterine and upper vaginal cavities. Surgical intervention conformed the diagnosis of a concurrent imperforate hymen and transverse vaginal septum, echoing the imaging findings of haematocolpometra. Her tumour marker levels gradually returned to normal after surgery. This rare case of concomitant imperforate hymen and transverse vaginal septum highlights that haematocolpometra, a benign disease that might mimic malignancy, should be taken into consideration in any adolescent females with an abdominal mass and amenorrhoea to ensure an early diagnosis and timely appropriate management.
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