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Laser-induced metal deposition on InP
Classified abstracts
561 O-561 9
24. LEAK DETECTORS
AND LEAK DETECTION
24 5610. Bebavior of small leaks in the presemze of liquid or gaseous helium at 4.2 K. (USA) Increased present day use of cryogenics necessitates an understanding of
the behaviour of small leaks at liquid helium temperatures. Little is to be found in the literature except that related to super-fluid effects in the range 1.4 to 2.9 K. We report the results of an investigation on the hehaviour of two small leaks (leak rates in the vicinity of 2 x IO-’ atm cc air s-’ at room temperature) at 4.2 K in contact with gaseous as well as liquid helium. In both cases, a significant increase in the leak rate was found when the leaks were in contact with liquid helium at 4.2 K. The observed hehaviour is explained using a model based on the changes in the physical . _ properties of helium with temperature. S Sinbaroy and W J Lange, J Vat Sci Technol, 26 (4) 1982, 978-981 24 5611. metbods for calibration of standard leaks. (USA) The Sandia Laboratories Standards Department is currently using the comparison, P AV, and accumulate-dump methods to calibrate standard leaks. The comparison method may be used in the range from 10es to lo-* atm cm3 s-i with a maximum uncertainty of 10%. The P AV method can be used for fundamental calibration of faster leaks in the range from lo-’ to 10-s atm cm3 s-’ with a maximum uncertainty of 5%. Finally the accumulate-dump method can be used to fundamentally calibrate leaks in the range from 10e4 to lo-“atm cm3 s-’ with uncertainties ranging from 5 to 20%. The purpose of this paper is to introduce these three calibration methods with an analysis of the errors involved. These methods are reviewed and compared with other leak calibration methods. M V Iversoo and J L Hartley, J Vat Sci Tech&, 36 (4) 1982,982-985.
25. HEATING
EQUIPMENT
AND THERMOMETERS
25 5612. A vacuum differential thermal analysis apparatus. (GB) A vacuum differential thermal analysis apparatus is described which can
be used up to 1ooo”C. A unique feature of the design is the facility for changing the sample with minimum disturbance to the heating and cooling systems. To test the equipment the magnetic transition in pure nickel has been investigated utilizing the change in specific heat at the transition point. S Nibols and F Laobavirojana, J Phys E: Sci Insrrum, 15 (5) 1982, 506-507.
III. Vacuum
AND DEPOSITION
5613. Highly stabilized bousing. (GB)
evaporation
IN V,4CUO
sources in a water-cooled
30 S615. A simple model for the hysteretic hehavior of ZnS:Mn thin film electroluminescent devices. (USA) A model is proposed for the observed hysteretic behaviour of ac-coupled ZnS: Mn thin-film electroluminescent devices. The following mechanisms are invoked: (1) tunnel injection from ZnSdielectric interfaces (U> lo6 V cm-‘), (2) electron-hole pair generation, (3) deep trapping of holes, leading to space-chargeformation, (4) charge storage at the ZnS-dielectric interfaces, and (5) direct recombination of injected electrons and trapped holes. When these mechanisms are combined in a self-consistent numerical simulation model, a bistability ofcharge transfer versus applied voltage is obtained which exhibits many of the characteristics of the observed device behaviour. Experimental evidence in support of the individual assumptions is also discussed. W E Howard et al, J Appl Phys.53 (1). 1982, 639447. 30 5616. SIC thin-film thermistor. (GB) A thermistor using a sputtered Sic film has been developed as a temperature-sensing device which is able to detect temperatures accurately over the wide range of 36300°C. The thermistor has a unique characteristic in that the B constant increases linearly with an increase of temperature. The typical values of the B constant increase from 1950 K at 50°C to 3080 K at 25OC. From this unique characteristic, the temperature dependence of resistance was calculated with high accuracy by an experimental equation. The thermistor consists of a thermistor element and a package. The thermistor element comprises the Sic film temperature sensor. The package comprises a small glass tube in which the thermistor element is sealed heremetically. The characteristics of the thermistor are very stable for long periods under various test condition.
(Jaw)
Takeshi Nagai et al, J Phys E: Sci Insrrum, 15 (5) 1982, 520-524. 5617. Pbotodeposition
30 of metal films with ultraviolet laser light. (USA)
A technique for maskless writing of metal films with submicrometer dimensions is described. An ultraviolet beam from a cw or pulsed laser is used to photodissociate an organometallic gas near a gas-solid interface. The liberated metal atoms then condense in an area of dimensions comparable to the laser spot size. Experiments which elucidate the essential physics of the process have been performed.
applications
30,EVAPORATION
grow together to form smooth platinum films -0.5 pm thick. Failure to form deposits at low laser powers indicates that platinum deposition occurs via a thermal mechanism. Auger electron analysis indicates that the platinum deposits are free of oxygen and chlorine contamination. Preliminary results also indicate that this technique may be used to deposit platinum on GaAs, nickel on InP (using aqueous NiSO, solutions) and gold on InP (using both aqueous and methanolic HAuCI, solutions). Platinum and gold deposits on InP exhibit ohmic behaviour. R F Karlicek et al, J Appl Phys, 53 (2), 1982, 1084-1090.
D J Ebrlicb, J Vat Sci Tech&, 30 carousel
The construction of a water-cooled housing for highly stabilized evaporation sources used in uhv for preparation of ultrathin metal films is described. Five different sources, which can be rotated one-by-one into position, give a perpendicular beam flux relative to the substrate surface. The design and performance of two highly stabilized metal evaporation sources with crucibles of graphite and boron nitride respectively are described. The temperature stability and decomposition of the graphitetype source are presented and discussed in detail. Furthermore the construction and experimental details are given for a high-purity carbon evaporation source exploiting the electron bombardment technique. (Sweden) S H Norrman et al, J Phys E: Sci Insrrum, 15 (7). 1982, 731-735.
21 (I), 1982, 23-32.
30 5618. Growth of HgCdTe films by laser induced evaporation and deposition. (USA)
Hg,_,Cd,Te films were deposited on CdTe (111) A, Si, and Al,O, substrates by evaporating from either (HgTe), J(CdTe), mixtures or Hg, _.Cd,Te bulk crystals with a pulsed YAG:Nd laser. Under this unique way of heating, the evaporation is congruent. Films were deposited at different substrate temperatures in a Hg partial pressure. The asdeposited films were stoichiometric and exhibit a strong (11 I) texture. As-grown films are n-type with electron mobility as high as 2 x IO4cm’/V-s at 77 K. J T Cheung and D T Cheung, J Vat Sci Techd, 21 (l), 1982, 182-186. 30 5619. Monte Carlo simulation of the growth of A, _J, layers on lattice
30 metal deposition on InP. (USA)
matched substrates in molecular heam epitaxy. (USA) We report some results of the first study of the influence of growth
It has been demonstrated that platinum can be deposited on p-type, n-type and undoped InP via pulsed laser irradiation of polished substrates immersed in an aqueous solution of chloroplatinic acid. Pulsed laser intensities sufficient to initiate thermal decomposition of the InP surface, yet below the threshold at which gross surface damage occurs, cause elemental platinum to be deposited on the surface. The platinum deposits in the form of rectangular islands on the (100) surface and trigonal structures on the (111) InP surface Under certain conditions, the islands
parameters on the nature of alloy films grown under ultrahigh vacuum deposition techniques such as MBE. Monte Carlo methods are employed to elucidate the interplay between rate of impingement, sticking coefficients (S) and surface mobilities (p) in governing disorder and clustering effects. The local environment, and consequently coverage dependence of S and p, are found to significantly influence the growth process and the nature of the resulting film. J Singh and A Madhukar, J Vat Sci Technol, 20 (3). 1982, 716719.
5614. Laser-induced
416
561 O-561 9
24. LEAK DETECTORS
AND LEAK DETECTION
24 5610. Bebavior of small leaks in the presemze of liquid or gaseous helium at 4.2 K. (USA) Increased present day use of cryogenics necessitates an understanding of
the behaviour of small leaks at liquid helium temperatures. Little is to be found in the literature except that related to super-fluid effects in the range 1.4 to 2.9 K. We report the results of an investigation on the hehaviour of two small leaks (leak rates in the vicinity of 2 x IO-’ atm cc air s-’ at room temperature) at 4.2 K in contact with gaseous as well as liquid helium. In both cases, a significant increase in the leak rate was found when the leaks were in contact with liquid helium at 4.2 K. The observed hehaviour is explained using a model based on the changes in the physical . _ properties of helium with temperature. S Sinbaroy and W J Lange, J Vat Sci Technol, 26 (4) 1982, 978-981 24 5611. metbods for calibration of standard leaks. (USA) The Sandia Laboratories Standards Department is currently using the comparison, P AV, and accumulate-dump methods to calibrate standard leaks. The comparison method may be used in the range from 10es to lo-* atm cm3 s-i with a maximum uncertainty of 10%. The P AV method can be used for fundamental calibration of faster leaks in the range from lo-’ to 10-s atm cm3 s-’ with a maximum uncertainty of 5%. Finally the accumulate-dump method can be used to fundamentally calibrate leaks in the range from 10e4 to lo-“atm cm3 s-’ with uncertainties ranging from 5 to 20%. The purpose of this paper is to introduce these three calibration methods with an analysis of the errors involved. These methods are reviewed and compared with other leak calibration methods. M V Iversoo and J L Hartley, J Vat Sci Tech&, 36 (4) 1982,982-985.
25. HEATING
EQUIPMENT
AND THERMOMETERS
25 5612. A vacuum differential thermal analysis apparatus. (GB) A vacuum differential thermal analysis apparatus is described which can
be used up to 1ooo”C. A unique feature of the design is the facility for changing the sample with minimum disturbance to the heating and cooling systems. To test the equipment the magnetic transition in pure nickel has been investigated utilizing the change in specific heat at the transition point. S Nibols and F Laobavirojana, J Phys E: Sci Insrrum, 15 (5) 1982, 506-507.
III. Vacuum
AND DEPOSITION
5613. Highly stabilized bousing. (GB)
evaporation
IN V,4CUO
sources in a water-cooled
30 S615. A simple model for the hysteretic hehavior of ZnS:Mn thin film electroluminescent devices. (USA) A model is proposed for the observed hysteretic behaviour of ac-coupled ZnS: Mn thin-film electroluminescent devices. The following mechanisms are invoked: (1) tunnel injection from ZnSdielectric interfaces (U> lo6 V cm-‘), (2) electron-hole pair generation, (3) deep trapping of holes, leading to space-chargeformation, (4) charge storage at the ZnS-dielectric interfaces, and (5) direct recombination of injected electrons and trapped holes. When these mechanisms are combined in a self-consistent numerical simulation model, a bistability ofcharge transfer versus applied voltage is obtained which exhibits many of the characteristics of the observed device behaviour. Experimental evidence in support of the individual assumptions is also discussed. W E Howard et al, J Appl Phys.53 (1). 1982, 639447. 30 5616. SIC thin-film thermistor. (GB) A thermistor using a sputtered Sic film has been developed as a temperature-sensing device which is able to detect temperatures accurately over the wide range of 36300°C. The thermistor has a unique characteristic in that the B constant increases linearly with an increase of temperature. The typical values of the B constant increase from 1950 K at 50°C to 3080 K at 25OC. From this unique characteristic, the temperature dependence of resistance was calculated with high accuracy by an experimental equation. The thermistor consists of a thermistor element and a package. The thermistor element comprises the Sic film temperature sensor. The package comprises a small glass tube in which the thermistor element is sealed heremetically. The characteristics of the thermistor are very stable for long periods under various test condition.
(Jaw)
Takeshi Nagai et al, J Phys E: Sci Insrrum, 15 (5) 1982, 520-524. 5617. Pbotodeposition
30 of metal films with ultraviolet laser light. (USA)
A technique for maskless writing of metal films with submicrometer dimensions is described. An ultraviolet beam from a cw or pulsed laser is used to photodissociate an organometallic gas near a gas-solid interface. The liberated metal atoms then condense in an area of dimensions comparable to the laser spot size. Experiments which elucidate the essential physics of the process have been performed.
applications
30,EVAPORATION
grow together to form smooth platinum films -0.5 pm thick. Failure to form deposits at low laser powers indicates that platinum deposition occurs via a thermal mechanism. Auger electron analysis indicates that the platinum deposits are free of oxygen and chlorine contamination. Preliminary results also indicate that this technique may be used to deposit platinum on GaAs, nickel on InP (using aqueous NiSO, solutions) and gold on InP (using both aqueous and methanolic HAuCI, solutions). Platinum and gold deposits on InP exhibit ohmic behaviour. R F Karlicek et al, J Appl Phys, 53 (2), 1982, 1084-1090.
D J Ebrlicb, J Vat Sci Tech&, 30 carousel
The construction of a water-cooled housing for highly stabilized evaporation sources used in uhv for preparation of ultrathin metal films is described. Five different sources, which can be rotated one-by-one into position, give a perpendicular beam flux relative to the substrate surface. The design and performance of two highly stabilized metal evaporation sources with crucibles of graphite and boron nitride respectively are described. The temperature stability and decomposition of the graphitetype source are presented and discussed in detail. Furthermore the construction and experimental details are given for a high-purity carbon evaporation source exploiting the electron bombardment technique. (Sweden) S H Norrman et al, J Phys E: Sci Insrrum, 15 (7). 1982, 731-735.
21 (I), 1982, 23-32.
30 5618. Growth of HgCdTe films by laser induced evaporation and deposition. (USA)
Hg,_,Cd,Te films were deposited on CdTe (111) A, Si, and Al,O, substrates by evaporating from either (HgTe), J(CdTe), mixtures or Hg, _.Cd,Te bulk crystals with a pulsed YAG:Nd laser. Under this unique way of heating, the evaporation is congruent. Films were deposited at different substrate temperatures in a Hg partial pressure. The asdeposited films were stoichiometric and exhibit a strong (11 I) texture. As-grown films are n-type with electron mobility as high as 2 x IO4cm’/V-s at 77 K. J T Cheung and D T Cheung, J Vat Sci Techd, 21 (l), 1982, 182-186. 30 5619. Monte Carlo simulation of the growth of A, _J, layers on lattice
30 metal deposition on InP. (USA)
matched substrates in molecular heam epitaxy. (USA) We report some results of the first study of the influence of growth
It has been demonstrated that platinum can be deposited on p-type, n-type and undoped InP via pulsed laser irradiation of polished substrates immersed in an aqueous solution of chloroplatinic acid. Pulsed laser intensities sufficient to initiate thermal decomposition of the InP surface, yet below the threshold at which gross surface damage occurs, cause elemental platinum to be deposited on the surface. The platinum deposits in the form of rectangular islands on the (100) surface and trigonal structures on the (111) InP surface Under certain conditions, the islands
parameters on the nature of alloy films grown under ultrahigh vacuum deposition techniques such as MBE. Monte Carlo methods are employed to elucidate the interplay between rate of impingement, sticking coefficients (S) and surface mobilities (p) in governing disorder and clustering effects. The local environment, and consequently coverage dependence of S and p, are found to significantly influence the growth process and the nature of the resulting film. J Singh and A Madhukar, J Vat Sci Technol, 20 (3). 1982, 716719.
5614. Laser-induced
416