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VNU JOURNAL OF SCIENCE, Nat Sci., t.XVI, PREPARATION SOME INVESTIGATION PROPERTIES n-TYPE OF THIN Bi,(Te, Se), Nguyen Institute of Cryptography, - 2000 AND THERMOELECTRIC ON n°4 SEMICONDUCTIVE FILM AND Duy OF SENSORS P-TYPE BASED (Bi, Sb),Te,; Phuong Department of Goverment's Dao Khac An top secret affairs Laboratory of R & D of Sensor, Institute of Materials Science Ta Dinh Canh, Pham Quoc Faculty of Physics Trieu College of Natural Sciences, Hanoi National University Abstract: In the thermoelectric engineering, many cases it is neccessary to measure temperature of the objects without contacting with them The temperature can be measi by using the sensors we present that are sensitive infrared the technology for preparation radiation from of thermo-couple the objects based on In this pa n - type Biz(Te,.£ and p- type (Bi, Sb)2Te3 thin films Some their properties such as: e vs T, noise fea are determined The prepared sensors can be used to make the equipment for far measu of temprature Introduction In thermal temperature is infrared materials technology, of distant object a popular problem If the object is the is not measurement brightly burning, of the most non-con of its radia Infrared radiation sensors are usually made of thermoelectric semiconduc The sensitivity of sensors usually is very high because it has a very Ì: coefficient of thermoelectric as compared to other metal materials The object temperature is determined by measuring the total energy which is diated in the form of electric signals Sensors operate on Seebeck effect An advant of this type of sensor is that it can record weak radiation of 1079 + 107!° w in av infrared band In this report, we will demonstrate the semiconducting thin filter thermoelec sensors which comprise components They are Bi2(Te, Se)3 of m type and of pt (Bi, Sb)2Te3 and made of highly-pure evaporation in vacuum To improve thermal batteries’s respective quality, thin materials film by the method sensors are first of ther made of si materials and then of and element mixtures in order to have the suitable carn density and a maximum temperature difference between the hot and cold source [1} 32 tparation and investigation of some properties of semiconductive The noise of infrared sensors is also taken into consideration to improve 33 sensor lity and to detect distant weak radiation Experimental, Sensors | system (Te, results and discussion are produced by method of thermal evaporation The sensors have several thermoelectric Se); and of p type (Bi, $b)2T es in asteroid in vacuum using German semi-conductor couples of n type series connection (Fig.1) on plastic form The plastic platform is 0.1 mm kk and has its surface thoroughly ited before it is put in vacuum fe the thermoelectric source of the sensor film to The concentrates le the asterism and is electrically ilated The cold source is good fact with open air by parallel tion with a copper | ring The film’s thickness is deter- ed by optical interference fs thickness is about The 1,5 jem The sensor’s hot source is on focus of concave mirror (Fig.2) § makes sensor sizes very small, dinner diameter @ = 3mm and tr diameter @ = 12mm, which lides thermo-couptes in series Fig.1: Photographs of IR sensor based on hection n-type Bi2(Te, Se)3 and p-type (Bi, Sb),Tes The concave mirror in the op- lamplifier is in fact an optical sig- This gives extra sen- ity to the sensor The thermotric index of film of n-type Bip j Se)s and of p-type (Bi, $b) Tes Babea te by the method in temperature difference be fn filter ends is AT = 3-+4°C, hl cords and the blocks to difhtiate and stabilize temperature made of lead The whole system fell insulated from ditions environment [2] Nữ Ỉ a a , ` e co \ : \ | "` =] » stem Fig.2: Structure of sensor unit (2) concave mirror; (1) sensor: (3) diaphrams Nguyen 34 Dao Phuong, Duy Khac From experimental curves in Fig.3 and 4, the œ index at 20°C is inferred as ¢ —92uV/°C, and ap = +171uV/°C The experiments show that linear recurrence is more accurate than log funct recurrence so it doesn’t correspond to normal semiconductor rules This maybe ca by a slight change in carriers density as a result of temperature variation or perhap: temperature change is too small for the dependence a =f(logn) to appear clearly 178 IK") f (HV/ mì t6 Ì ‡ 1Ì 174 : ts ; i Obes Ge eee 22 s os! ‡ ee s art ị °° oer oer os} re eon 24 tứC) a ; 27 Fig.3: Dependent of a-index of p type(Bi,Sb)2Te; film on temperature (avi) ‡ He ute Ỉ 22 ° a lộ ° ni on SG 23 nh 24 he 25 Fig.4: Dependent of a-inde> of n type Bi2(Te,Se); film on temp However, the a index measured by extrapolating from room temperature is quite similar to the announced results for the dimensional devices in [3] With sensors as Fig.1, the e.m.f is determines according to the tem- perature of a conical coal piece at a constant distance from the sensor (by non-contact method) as shown in Fig.5 on a X-Y recorder So with reasonable accuracy, this can be considered as unfiltering wide band infrared sensors In order to identify the cordsensor contact, the votage-amperage quality is measured on DLTS8000 The finding is shown on Fig as a straight line, which indicates that the cord-sensor contact is omic Tey Fig.5: Dependent of e.m.f on perature (of the conical coal piece) The equivalent circuit of the sensor, therefor can be described as shown + Equivalent circuit and noise sensor: in Fig paration and In which investigation Roy, R.2 of some are the contact properties resittivity of semiconductive between the cord and 35 the sensor; T,X) is the branch resitivity of p-type and n-type of thermoelectric films in continual hection Current Be [u81 Ra 8.8 1.8 Bias Fig 6: The voltage-amperage quality of infrared sensor (U2 4,774) Fig.7:The equivalent circuit of the sensor In ordinary sensor, total noise has many types of of components whose source is the lcal coal piece.either known or unknown Based on our diagram on infrared radiation sensors, total noise may ents such as: | xã | du ee “otal = "thermal „= oise Spectrum The spectrum T2 1ó fghort T ŸFlieker + °°" of sensor: of total feasured on FSEA30 noise on te Spectrum when sensors are pe pare llyser at the Institute of Mate} Science include com- a ate Ome na baad not fable and when : infrared radia| | sensors are available Results showed that within the uency band from Hz + 250 y% there are a lot of noise eleits in different frequencies that tribute to the total noise, Comng to the Spectrum of thermal e from radiators and studying in ltrum analyzer, we can see that t are of similar (es) forms Conse- a atly, typical noise is mainly ther- Fig describees 1/f noise of ors measured by Lock-In-Amplifier Fig.8: 80 DSP a- Floor noise; b- White noise; c- Noise of sensor > si š seen tn this As can be seen in this Noise spectrum density: : fs ee 36 Nguyen Duy Phuong, Dao figure 1/f noise apparently strengthens within the low frequency band concerned electric with surface conditions of sensors, wich branches and conductor-wire does not depend on frequency but on higher frequency band is the meeting thermal electric is more likely attricbuted A This noise is me point web contacts Khac the between the1 noise spect to thermal and short r 85E-13, m=1,66 548E-13, m=1.67 Fig.9: 1/f noise of sensors Conclusion The operation of multi component Stefan-Boltzmann function stable enough their them and Xuan noise to determine distant Acknowledgment: Viet MSc within Faculty an acceptable error has been thermal Authors preliminary sensors range assessed, corresponds The sensors which brings well tc are sensi chances t« threshold would like to thank of physics - Ha Institute of Materials Science thermoelectric for their Noi to Prof National help in nc Dam Univer Trung Don and Ng) Nguyen Trung Kien measuring REFERENCES B.M.Golzman (2) 19 tussian) L.V.Vu, T.D.Canh, thermoelectric N.An, D.T.Don, P.N.Hai the Bi - Te thermoelectric thin film VNU, 12 3] Semiconducting + based IFRa BizTe3, - Red “Science”, Radiative Journal of Science, Nat.See., Mo: sensor 191 16 D.D.Thong, V.Linh, Noi 1990, p 84 + 89 P.V.Uyen Procedings of the science conference of HP( + ‘eparation and investigation (4) N.T-Binh and D.K.An, diode of some properties of semiconductive Some noise features and noise equivalent circuit of photo- using in measurement Vol.9, (1999) pp 51+ 60 and optical instrumenrs Communications [5] A.Van Der Ziel Fluctuation Phenonmena in Semiconductors [6] S.M Sze Physics of Semiconductor Devies New York, 1981 P CHI KHOA HOC ĐHQGHN, 37 KHTN, t.XVI, n4 London, in Physics, 1959 - 2000 NGHIÊN CỨU CHẾ TẠO VÀ KHẢO SÁT MỘT SỐ TÍNH CHẤT CỦA SENSOR NHIỆT ĐIỆN TREN CƠ SỞ ¡¿( e)3 LOẠI ø VÀ (Bi, Sb)¿Tes LOẠI p Nguyễn Duy Phương Học viện Kỹ thuật Mật mã - Ban Cơ yếu Chính phủ Đào Khắc An Phòng Nghiên cứu Phát triển Sensor Viện Khoa học Vật liệu, Trung tân KHTN & ƠNQG Tạ Đình Cảnh, Phạm Quốc Triệu Khoa Ly, Đại học Khoa học Tìr nhiên - ĐHQG Hà Nội Trong kỹ thuật nhiệt điện, nhiều trường hợp cần đo nhiệt độ vật mà không | tiếp xúc với vật Người ta dùng sensor nhận xạ hồng ngoại it tir vat, từ biết nhiệt độ vật Trong báo này, trình bày ig nghé ché tao Sensor Bi(Te, Se)3 loai n va (Bi, $b)2Te3 loại p phương pháp ! bay nhiệt chân khơng Một số tính chất sensor khảo sát r: phụ thuộc suất điện động e vào nhiệt độ 7, đặc trưng nhiễu Các kết bước đầu cho thấy triển vọng ứng dụng sensor vào thiết bị đo ệt độ từ xa khách quan ... Procedings of the science conference of HP( + ‘eparation and investigation (4) N.T-Binh and D.K.An, diode of some properties of semiconductive Some noise features and noise equivalent circuit of photo-... investigation Roy, R.2 of some are the contact properties resittivity of semiconductive between the cord and 35 the sensor; T,X) is the branch resitivity of p-type and n-type of thermoelectric films in continual...tparation and investigation of some properties of semiconductive The noise of infrared sensors is also taken into consideration to improve 33 sensor lity and to detect distant weak